NASA Cassini Image of Prometheus and its Flock of Ring Particles http://www.spaceref.com/news/viewsr.html?pid=14097 "In its own way, the shepherd moon Prometheus (102 kilometers, 63 miles across) is one of the lords of Saturn's rings. The little moon maintains the inner edge of Saturn's thin, knotted F ring, while its slightly smaller cohort Pandora (84 kilometers, or 52 miles across) guards the ring's outer edge." After a Trio of Explosions Scientists say Supernova is Imminent

http://www.spaceref.com/news/viewpr.html?pid=15170 "Three powerful recent blasts from three wholly different regions in space have left scientists scrambling. The blasts, which lasted only a few seconds, might be early alert systems for star explosions called supernovae, which could start appearing any day."

Massive Merger of Galaxies is the Most Powerful on Record http://www.spaceref.com/news/viewpr.html?pid=15119 "An international team of scientists, led by a NASA- funded researcher, announced today, they observed a nearby head-on collision of two galaxy clusters. The clusters smashed together thousands of galaxies and trillions of stars. It is one of the most powerful events ever witnessed. Such collisions are second only to the Big Bang in total energy output."

La luna de Júpiter, Io, lanza pequeñas partículas volcánicas a naves cercanas. Septiembre 14, 2004: El satélite de Júpiter, Io, está salpicado con volcanes, los más calientes y activos de nuestro sistema solar. Las fumarolas arrojan siseantes penachos de gas y polvo a alturas superiores a los 400 km. Aparecen, estallan, y desaparecen, para luego reaparecer. El ciclo se repite continuamente. http://ciencia.msfc.nasa.gov/headlines/y2004/14sep_jupiterdust.htm?list1176985

Ocean Waves May Be Source of Earth's Hum By Glennda Chui 09/30/04 11:12 AM PT The pounding of huge waves on the ocean floor sets the Earth humming in a phenomenon known as free oscillation, Barbara Romanowicz, a seismologist at the University of California-Berkeley, reported in the journal Nature. Sybase ASE Linux Express Edition – FREE The first enterprise-class commercial database that can take you from pilot to deployment for zero dollars and zero risk. Scientists think they have found the source of a mysterious hum that reverberates through the Earth, too low for human ears to hear. They used to think it came from earthquakes; a big quake will set the whole planet ringing like a bell. But even when there are no big quakes, the hum continues, a slow, steady slosh of waves around the planet. Now, with instruments in California and Japan, scientists have pinpointed the source. The hum, they say, starts in the oceans, when winter storms whip the waves into a frenzy. Deep Ocean Waves "These waves interact with each other to create longer waves that reach deep into the ocean, all the way to the ocean floor," said Barbara Romanowicz, a seismologist at the University of California-Berkeley. It is the thumping of those waves on the bottom, like the pounding of a drum, that sets the Earth vibrating in a phenomenon known as free oscillation, she said. She and graduate student Junkee Rhie put forth their explanation in Thursday's issue of the journal Nature. Gregory Beroza, a geophysicist at Stanford University, said he found the report convincing. "It's just interesting, a new phenomenon that begs to be explained," he said. Annoying Hum The hum has fascinated scientists since its discovery six years ago by a group in Japan. Its vibrations consist of long, slow seismic waves that raise the ground by a fraction of an inch as they go by. It takes five minutes for two of these waves to pass a given point. They put out very little power -- about as much as a couple of 100-watt light bulbs, Romanowicz said. Although these waves crisscross the planet all the time, people cannot feel or hear them. In musical terms, the sound would be about 16 octaves below middle C. Which may be just as well. If the hum were shifted up into the range of human hearing, it would be a cacophony of noise, said professor Toshiro Tanimoto, a geophysicist at UC-Santa Barbara. The tones "are never in harmony so it would be horrible, probably," he said. "More like modern music" than baroque. Pinpointing Origins To figure out where the hum starts, Romanowicz and Rhie looked at readings from about two dozen seismic instruments in California and Japan. They found that the hum originated in the northern oceans in winter and in the southern oceans in the summer, which is the winter storm season there. Romanowicz said she wants to check the seismic instruments to see if the recent string of hurricanes had any effect on the hum. "Even though they're very strong at the surface, and have devastating consequences when they land, they're very localized. They cover only a very narrow swath," she said of hurricanes. So her hunch is that they did not -- "but it has to be checked." http://www.technewsworld.com/story/37013.html

Pinhole Camera to Image New Worlds based on Colorado report Estimates suggest that up to a quarter of all stars have planets. Credit: NASA/ STScI/ ESA An advanced University of Colorado at Boulder proposal for further study describes how existing technologies can be used to study planets around distant stars with the help of an orbiting "starshade." The concept by CU-Boulder Professor Webster Cash of the Center for Astrophysics and Space Astronomy was one of 12 proposals selected for funding Sept. 28 by the NASA Institute for Advanced Concepts, or NIAC. Cash's proposal details the methods needed to design and build what essentially is a giant "pinhole camera" in space. The football field-sized starshade would be made of thin, opaque material and contain an aperture, or hole, in the center roughly 30 feet in diameter to separate a distant planet's light from the light of its adjacent parent star, Cash said. A detector spacecraft equipped with a telescope would trail tens of thousands of miles behind the orbiting starshade to collect the light and process it. Such a system could be used to map planetary systems around other stars, detect planets as small as Earth's moon and search for "biomarkers" such as methane, water, oxygen and ozone. Known as the New Worlds Imager, the system also could map planet rotation rates, detect the presence of weather and even confirm the existence of liquid oceans on distant planets, he said. Scene from a moon orbiting the extra-solar planet in orbit around the star HD70642. Credit:David A. Hardy, astroart.org (c) pparc.ac.uk "In its most advanced form, the New Worlds Imager would be able to capture actual pictures of planets as far away as 100 light-years, showing oceans, continents, polar caps and cloud banks," said Cash. If extra-terrestrial rainforests exist, he said, they might be distinguishable from deserts. "To me, one of the most interesting challenges in space astronomy today is the detection of exo-solar planets," said Cash. "We have created an affordable concept with very practical technology that would allow us to conduct planet imaging in visible and other wavelengths of light." The beauty of the pinhole as an optical device is that it functions as an almost perfect lens, said Cash, who is a professor in CU-Boulder's astrophysical and planetary sciences department. 'This device would remove the limiting problem of light scattered from the parent star due to optical imperfections." The successful proposal was authored by Cash, Princeton University's Jeremy Kasdin and Sara Seager of the Carnegie Institution of Washington. Nine other proposal advisers from universities and industry contributed to the New Worlds Imager concept, said Cash. NIAC was created in 1998 to solicit revolutionary concepts from people and organizations outside the space agency that could advance NASA's missions. The winning concepts, chosen because they "push the limits of known science and technology," are expected to take at least a decade to develop if they eventually are selected for a mission flight, according to NASA. In 1999, Cash headed a winning NIAC proposal for a new, powerful x-ray telescope technology that will allow astronomers to peer into the mouths of black holes. That telescope package is now under development by NASA as the multi-million dollar MAXIM mission and is slated for launch next decade. HD 28185 b is the first exoplanet discovered with a circular orbit within its star's habitable zone. Astrobiology: the study of how life begins and evolves - that is, where did we come from? Does life exist elsewhere in the universe - are we alone? And, what is life's future on Earth and beyond - where are we going in space Credit: STScI Digitized Sky Survey Other concepts funded in 2004 by NIAC include a proposal for a lunar space elevator, new super-conducting magnet technology for astronaut radiation protection and a magnetized beam plasma-propulsion system. Teams that submitted winning proposals to NIAC this year were awarded $75,000 for a Phase 1, six-month viability study. Those proposals that go on to win approval for Phase 2 studies next year by the space agency will be funded with up to $400,000 for two additional years, according to NASA. "We are thrilled to team up with imaginative people from industry and universities to discover innovative systems that meet the tremendous challenge of space exploration and development," said NIAC Director Robert Cassanova. Cassanova also is a member of the Universities Space Research Association, which administers NIAC for NASA. http://www.astrobio.net/news/article1226.html

New Star-Type Stillborn based on NOAO report A close-up view of the EF Eridanus system as it might appear today given that most of the radiation emitted by the system is in the infrared part of the spectrum and not visible to the human eye. The banner image illustrates the onset of mass transfer some 500 million years ago when the donor object (right), began losing mass to the compact yet more massive white dwarf companion (left). Credit: NOAO Astronomers using the Gemini North and Keck II telescopes have peered inside a violent binary star system to find that one of the interacting stars has lost so much mass to its partner that it has regressed to a strange, inert body resembling no known star type. Unable to sustain nuclear fusion at its core and doomed to orbit with its much more energetic white dwarf partner for millions of years, the dead star is essentially a new, indeterminate type of stellar object. "Like the classic line about the aggrieved partner in a romantic relationship, the smaller donor star gave, and gave, and gave some more until it had nothing left to give," says Steve B. Howell, an astronomer with Wisconsin-Indiana-Yale-NOAO (WIYN) telescope and the National Optical Astronomy Observatory, Tucson, AZ. "Now the donor star has reached a dead end - it is far too massive to be considered a super-planet, its composition does not match known brown dwarfs, and it is far too low in mass to be a star. There's no true category for an object in such limbo." The binary system, known as EF Eridanus (abbreviated EF Eri), is located 300 light-years from Earth in the constellation Eridanus. EF Eri consists of a faint white dwarf star with about 60 percent of the mass of the Sun and the donor object of unknown type, which has an estimated bulk of only 1/20th of a solar mass. Combining the light from the twin giant Mauna Kea telescopes. Credit:Keck Observatory Howell and Thomas E. Harrison of New Mexico State University made high- precision infrared measurements of the binary star system using the spectrographic capabilities of the Near Infrared Imager (NIRI) on the Gemini North telescope and NIRSPEC on Keck II, both on Mauna Kea in Hawaii, in December 2002 and September 2003, respectively. Supporting observations were made with the 2.1-meter telescope at Kitt Peak National Observatory near Tucson in September 2002. EF Eri is a type of binary star system known as magnetic cataclysmic variables. This class of systems may produce many more of these 'dead' objects than scientists have realized, says Harrison, co-author of a paper on the discovery to be published in the October 20 issue of the Astrophysical Journal. "These types of systems are not generally accounted for within the usual census figures of star systems in a typical galaxy," Harrison says. "They certainly should be considered more carefully." The white dwarf in EF Eri is a compressed, burnt-out remnant of a solar-type star that is now about the same diameter as the Earth, though it still emits copious amounts of visible light. Howell and Harrison observed EF Eri in the infrared because infrared light from the pair is naturally dominated by heat and longer wavelength emissions from the secondary object. Location of EF Eridanus in the southern constellation of Eridanus, the River. Although only visible in large infrared telescopes today, some 500 million years ago, this system might have been visible as a dim point of light to the naked eye. Credit:NOAO The scientific detective work to deduce the components of this binary system was complicated greatly by the cyclotron radiation emitted as free electrons spiral down the powerful magnetic field lines of the white dwarf. The white dwarf's magnetic field is about 14 million times as powerful as the Sun's. The resulting cyclotron radiation is emitted primarily in the infrared part of the spectrum. "In our initial spectroscopy of EF Eri, we noted that some parts of the infrared continuum light became about 2-3 times brighter for a time period, then went away. This brightening repeated every orbit, and thus had to have an origin within the binary," Howell explains. "We first thought the brightness change resulted from the difference between a heated side and a cooler side of the donor object, but further observations with Gemini and Keck instead pointed to cyclotron radiation. We 'see' this additional infrared component at the phases which occur when the radiation is beamed in our direction, and we do not see it when the beaming points in other directions." The 81-minute orbital period of the two objects was probably four or five hours when the mass transfer process began about five billion years ago. Originally, the secondary object may also have been similar in size to the Sun, with perhaps 50-100 percent of a solar mass. "When this interactive process of mass transfer from the secondary star to the white dwarf begin, and why it stopped, both remain unknown to us," Howell says. During this process, repeated outbursts and novae explosions were very likely. The physics of the process also caused the two objects to spiral closer to each other. Today, the two objects orbit each other at about the same separation as the distance from the Earth to the Moon. The donor object has regressed to a body with a diameter roughly equal to the planet Jupiter. The combined observing power of the Gemini 8-meter and Keck 10-meter telescopes and their large primary mirrors, which were essential to this research, Howell says, makes it clear that neither spectral features of the donor nor its composition match any known type of brown dwarf or planet. Derek Homeier (University of Georgia) created a series of computer models that attempt to replicate the conditions at EF Eri, but even the best of these do not match perfectly. The shape of the spectra indicate a very cool object (about 1,700 degrees Kelvin, equivalent to a cool brown dwarf), yet they do not have the same detailed shape or key features of brown dwarf spectra. The coolest normal stars (very low mass M-type stars) are about 2,500 degrees K, and Jupiter is 124 degrees K. The close-in "hot Jupiter" exoplanets detected indirectly by other astronomers using their gravitational effect on their parent stars are estimated to be 1,000-1,600 degrees K. There is a small chance that the EF Eri system could have originally consisted of the progenitor of the present-day white dwarf star and some sort of "super -planet" that survived the evolution of the white dwarf to result in the system observed now, but this is considered unlikely. "There are about 15 other known binary systems out there that may be similar to EF Eri, but none has been studied enough to tell," Howell says. "We are working on some of them right now, and trying to improve our models to better match the infrared spectra." -------------------------------------------------------------------------------- Co-authors of this paper on EF Eri are Paula Szkody of the University of Washington in Seattle, and Joni Johnson and Heather Osborne of New Mexico State. The WIYN 3.5-meter telescope is located at Kitt Peak National Observatory, 55 miles southwest of Tucson, AZ. Kitt Peak National Observatory is part of the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under a cooperative agreement with the National Science Foundation (NSF). http://www.astrobio.net/news/article1230.html

Motion of Material in the Early Universe Summary - (Oct 8, 2004) Researchers from Caltech have looked deep into space to a time when early material in the Universe was swirling towards the creation of galaxy clusters and superclusters. They did their measurements using an instrument in the Chilean Andes called the Cosmic Background Imager (CBI), which looks at the Universe when it was only 400,000 years old - a time before galaxies, stars, and planets had formed. By watching the motion of this material as it began forming larger structures, the researchers were able to confirm that dark matter and dark energy were having an effect even then. Full Story - Cosmologists from the California Institute of Technology have used observations probing back to the remote epoch of the universe when atoms were first forming to detect movements among the seeds that gave rise to clusters of galaxies. The new results show the motion of primordial matter on its way to forming galaxy clusters and superclusters. The observations were obtained with an instrument high in the Chilean Andes known as the Cosmic Background Imager (CBI), and they provide new confidence in the accuracy of the standard model of the early universe in which rapid inflation occurred a brief instant after the Big Bang. The novel feature of these polarization observations is that they reveal directly the seeds of galaxy clusters and their motions as they proceeded to form the first clusters of galaxies. Reporting in the October 7 online edition of Science Express, Caltech's Rawn Professor of Astronomy, and principal investigator on the CBI project, Anthony Readhead and his team say the new polarization results provide strong support for the standard model of the universe as a place in which dark matter and dark energy are much more prevalent than everyday matter as we know it, which poses a major problem for physics. A companion paper describing early polarization observations with the CBI has been submitted to the Astrophysical Journal. The cosmic background observed by the CBI originates from the era just 400,000 years after the Big Bang and provides a wealth of information on the nature of the universe. At this remote epoch none of the familiar structures of the universe existed--there were no galaxies, stars, or planets. Instead there were only tiny density fluctuations, and these were the seeds out of which galaxies and stars formed under the hand of gravity. Instruments prior to the CBI had detected fluctuations on large angular scales, corresponding to masses much larger than superclusters of galaxies. The high resolution of the CBI allowed the seeds of the structures we observe around us in the universe today to be observed for the first time in January 2000. The expanding universe cooled and by 400,000 years after the Big Bang it was cool enough for electrons and protons to combine to form atoms. Prior to this time photons could not travel far before colliding with an electron, and the universe was like a dense fog, but at this point the universe became transparent and since that time the photons have streamed freely across the universe to reach our telescopes today, 13.8 billion years later. Thus observations of the microwave background provide a snapshot of the universe as it was just 400,000 years after the Big Bang--long before the formation of the first galaxies, stars, and planets. The new data were collected by the CBI between September 2002 and May 2004, and cover four patches of sky, encompassing a total area three hundred times the size of the moon and showing fine details only a fraction of the size of the moon. The new results are based on a property of light called polarization. This is a property that can be demonstrated easily with a pair of polarizing sunglasses. If one looks at light reflected off a pond through such sunglasses and then rotates the sunglasses, one sees the reflected light varying in brightness. This is because the reflected light is polarized, and the polarizing sunglasses only transmit light whose polarization is properly aligned with the glasses. The CBI likewise picks out the polarized light, and it is the details of this light that reveal the motion of the seeds of galaxy clusters. In the total intensity we see a series of peaks and valleys, where the peaks are successive harmonics of a fundamental "tone." In the polarized emission we also see a series of peaks and valleys, but the peaks in the polarized emission coincide with the valleys in the total intensity, and vice versa. In other words, the polarized emission is exactly out of step with the total intensity. This property of the polarized emission being out of step with the total intensity indicates that the polarized emission arises from the motion of the material. The first detection of polarized emission by the Degree Angular Scale Interferometer (DASI), the sister project of the CBI, in 2002 provided dramatic evidence of motion in the early universe, as did the measurements by the Wilkinson Microwave Anisotropy Probe (WMAP) in 2003. The CBI results announced today significantly augment these earlier findings by demonstrating directly, and on the small scales corresponding to galaxy clusters, that the polarized emission is out of step with the total intensity. Other data on the cosmic microwave background polarization were released just two weeks ago by the DASI team, whose three years of results show further compelling evidence that the polarization is indeed due to the cosmic background and is not contaminated by radiation from the Milky Way. The results of these two sister projects therefore complement each other beautifully, as was the intention of Readhead and John Carlstrom, the principal investigator of DASI and a coauthor on the CBI paper, when they planned these two instruments a decade ago. According to Readhead, "Physics has no satisfactory explanation for the dark energy which dominates the universe. This problem presents the most serious challenge to fundamental physics since the quantum and relativistic revolutions of a century ago. The successes of these polarization experiments give confidence in our ability to probe fine details of the polarized cosmic background, which will eventually throw light on the nature of this dark energy." "The success of these polarization experiments has opened a new window for exploring the universe which may allow us to probe the first instants of the universe through observations of gravitational waves from the epoch of inflation," says Carlstrom. The analysis of the CBI data is carried out in collaboration with groups at the National Radio Astronomy Observatory (NRAO) and at the Canadian Institute for Theoretical Astrophysics (CITA). "This is truly an exciting time in cosmological research, with a remarkable convergence of theory and observation, a universe full of mysteries such as dark matter and dark energy, and a fantastic array of new technology--there is tremendous potential for fundamental discoveries here" says Steve Myers of the NRAO, a coauthor and key member of the CBI team from its inception. According to Richard Bond, director of CITA and a coauthor of the paper, "As a theorist in the early eighties, when we were first showing that the magnitude of the cosmic microwave background polarization would likely be a factor of a hundred down in power from the minute temperature variations that were themselves a heroic effort to discover, it seemed wishful thinking that even in some far distant future such minute signals would be revealed. With these polarization detections, the wished-for has become reality, thanks to remarkable technological advances in experiments such as CBI. It has been our privilege at CITA to be fully engaged as members of the CBI team in unveiling these signals and interpreting their cosmological significance for what has emerged as the standard model of cosmic structure formation and evolution." The next step for Readhead and his CBI team will be to refine these polarization observations significantly by taking more data, and to test whether or not the polarized emission is exactly out of step with the total intensity with the goal of finding some clues to the nature of the dark matter and dark energy. The CBI is a microwave telescope array comprising 13 separate antennas, each about three feet in diameter and operating in 10 frequency channels, set up in concert so that the entire instruments acts as a set of 780 interferometers. The CBI is located at Llano de Chajnantor, a high plateau in Chile at 16,800 feet, making it by far the most sophisticated scientific instrument ever used at such high altitudes. The telescope is so high, in fact, that members of the scientific team must each carry bottled oxygen to do the work. The upgrade of the CBI to polarization capability was supported by a generous grant from the Kavli Operating Institute, and the project is also the grateful recipient of continuing support from Barbara and Stanley Rawn Jr. The CBI is also supported by the National Science Foundation, the California Institute of Technology, and the Canadian Institute for Advanced Research, and has also received generous support from Maxine and Ronald Linde, Cecil and Sally Drinkward, and the Kavli Institute for Cosmological Physics at the University of Chicago. In addition to the scientists mentioned above, today's Science Express paper is coauthored by C. Contaldi and J. L. Sievers of CITA, J.K. Cartwright and S. Padin, both of Caltech and the University of Chicago; B. S. Mason and M. Pospieszalski of the NRAO; C. Achermann, P. Altamirano, L. Bronfman, S. Casassus, and J. May all of the University of Chile; C. Dickinson, J. Kovac, T. J. Pearson, and M. Shepherd of Caltech; W. L. Holzapfel of UC Berkeley; E. M. Leitch and C. Pryke of the University of Chicago; D. Pogosyan of the University of Toronto and the University of Alberta; and R. Bustos, R. Reeves, and S. Torres of the University of Concepción, Chile. http://www.universetoday.com/am/publish/motion_material_early_universe.html?8102004

The 130 extrasolar planets discovered so far are in solar systems very different from our own, in which life-bearing planets like Earth are unlikely to exist. But an obscure characteristic of these planets and their stars has led astronomers to predict that our galaxy is brimming with solar systems like ours. The key to their prediction is something called metallicity. Extrasolar Planets: A Matter of Metallicity by Henry Bortman Astronomer Greg Laughlin studies extrasolar planets. Credit: Tim Stephens Astronomers have discovered more than 130 planets orbiting nearby stars in our galaxy. Although the solar systems they have found are very different from ours, by studying the planets that have been found - their masses, their orbits and their stars - they are uncovering intriguing hints that our galaxy may be brimming with solar systems like our own. According to Greg Laughlin, an assistant professor of astronomy and astrophysics at UC Santa Cruz, planet hunters can expect, over time, to find hundreds of nearby stars with Neptune-like planets circling them at about 5 AU. (One AU, or astronomical unit, is the distance between the sun and Earth. Jupiter orbits our sun at about 5 AU.) A solar system with a large planet at 5 AU, astronomers believe, is one in which a habitable terrestrial-sized planet could also safely exist. Laughlin's prediction comes from studying a characteristic of stars that, until a few years ago, few paid much attention to: metallicity. New stars form when vast clouds of interstellar dust and gas collapse. This dust and gas is mostly primordial hydrogen and helium, but it also contains a smattering of heavier elements, which astronomers call "metals" (even though non-astronomers don't normally think of all of these elements as metals). The metallicity of a star tells you what portion of its material is made of metals. And, says Laughlin, "the one true indicator of whether a star is likely to have a detectable giant planet is its metallicity." These hot Jupiters and eccentric Jupiters, as they are known, are the easiest types of planets to detect; almost all the planets discovered to date are of these two types. And "the vast majority of extrasolar planets that are known so far are around metal-rich stars." Scene from a moon orbiting the extra-solar planet in orbit around the star HD70642. Credit:David A. Hardy, astroart.org (c) pparc.ac.uk Here's why. When a metal-rich interstellar cloud collapses, it forms a metal-rich star. According to the core-accretion theory, the dominant theory of planetary formation, this abundance of heavy material also enables large rocky planetary cores to form relatively quickly, within a few million years. Once these cores reach 10 Earth masses or more, they begin attracting hydrogen and helium gas from the collapsing cloud; they become gas giants. How big these giants get depends on how much gas they attract. But the hydrogen and helium don't stick around forever. So timing is critical: only large rocky cores that form before the gas disappears become gas giants. Cores that grow too slowly - the lower the metallicity of the collapsing cloud, the more slowly the cores grow - can't grab any gas. "If the disk lifetime is 4 million years and it takes you 5 million years to build a core, then you're out of luck," says Laughlin. "But if you can get that core buildup time down to 2.5 million years, say, then there's still plenty of gas available." Both of these types of planets can be seen in our solar system. "The sun is a metal-rich star, but not dramatically so," Laughlin says. When our solar system was forming, there was enough heavy material around for Jupiter and Saturn to form their cores quickly. They got gas. Neptune and Uranus, however, didn't make it to the starting gate. There is a strong correlation between high solar metallicity and hot Jupiters. The picture is fuzzier, though, for eccentric Jupiters, planets with elongated elliptical orbits that have been found out to an average distance of about 3 AU from their stars. And it is fuzzier still for planets with orbits like Jupiter's. Planets out at 5 AU take more than a decade to complete their trips around their stars; astronomers have only begun to confirm their presence. HD 28185 b is the first exoplanet discovered with a circular orbit within its star's habitable zone. Credit: STScI Digitized Sky Survey But Laughlin thinks he knows what to expect once all the data are in: lots of Neptune-mass planets, with some as massive as Saturn, in Jupiter-like orbits. Why Neptunes? Metallicity. The majority of the stars that U.S.-based planet hunters are studying have a bit more than half the metallicity of the sun. That's enough to form a large rocky planet like Neptune. There's no time limit on Neptunes. But it's not enough to form a core quickly; it's not enough to become a gas giant. So what are the prospects of finding solar systems that contain Earth-like planets? Pretty good, according to Laughlin. The solar systems that have been found so far, the ones that contain hot Jupiters or eccentric Jupiters, probably don't contain habitable Earth-like planets. The motions of these closer-in giants prevent terrestrial planets from forming stable orbits in the habitable zone. But a solar system with a large planet in a circular orbit at 5 AU - even a Neptune-sized planet - is a solar system in which a habitable Earth-like planet could exist quite comfortably. Indeed, Laughlin believes that, when all the data are in, we'll have discovered hundreds of nearby stars with solar systems much like our own, although the majority of them will have a Neptune or a Saturn at 5 AU rather than a Jupiter. True, planet hunters haven't found any such planets yet. But that doesn't mean they're not there. Astronomers just haven't been looking long enough to confirm their presence. With current planet-hunting techniques, Laughlin says, "it's not like you discover a planet - boom!" - in a single observation. "The planets emerge gradually," as a result of many, many observations over time. So just how long will it take to find such worlds? Well, that's the unfortunate part of the story. Although astronomers have already begun to detect large planets in Jupiter-like orbits, it will take another 10 to 20 years to complete the census of planets orbiting at 5 AU around nearby stars. "The amount of patience that you have to exercise to get a true Jupiter analog is really enormously more than the amount of patience that you need to find and detect a hot Jupiter or an eccentric giant," Laughlin says. But considering that 10 years ago no-one knew for sure whether there was even a single planet around a star other than our sun, perhaps another 10 or 20 years isn't such a long time to wait. -------------------------------------------------------------------------------- Related Web Pages Coming Soon: Good Jupiters IAU Working Group on Extrasolar Planets The University of California Planet Search Project Astrobiology Magazine New Planets Transit Search Extrasolar Planets Encyclopedia Planet Quest (JPL) Kepler Mission Darwin Mission Space Interferometry Mission New Planets This article comes from Astrobiology Magazine http://www.astrobio.net/news/ The URL for this story is: http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1241

PRESS RELEASE Date Released: Tuesday, October 26, 2004 Source: Marshall Space Flight Center Chandra's Find of Lonely Halo Raises Questions About Dark Matter Dark matter continues to confound astronomers, as NASA‚s Chandra X-ray Observatory demonstrated with the detection of an extensive envelope of dark matter around an isolated elliptical galaxy. This discovery conflicts with optical data that suggest a dearth of dark matter around similar galaxies, and raises questions about how galaxies acquire and keep such dark matter halos. The observed galaxy, known as NGC 4555, is unusual in that it is a fairly large, elliptical galaxy that is not part of a group or cluster of galaxies. In a paper to be published in the November 1, 2004 issue of the Monthly Notices of the Royal Astronomical Society, Ewan O'Sullivan of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA and Trevor Ponman of the University of Birmingham, United Kingdom, use the Chandra data to show that the galaxy is embedded in a cloud of 10-million-degree-Celsius gas. This hot gas cloud has a diameter of about 400,000 light years, about twice that of the visible galaxy. An enormous envelope, or halo, of dark matter is needed to confine the hot cloud to the galaxy. The total mass of the dark matter halo is about ten times the combined mass of the stars in the galaxy, and 300 times the mass of the hot gas cloud. A growing body of evidence indicates that dark matter - which interacts with itself and "normal" matter only through gravity - is the dominant form of matter in the universe. According to the popular "cold dark matter" theory, dark matter consists of mysterious particles left over from the dense early universe that were moving slowly when galaxies and galaxy clusters began to form. "The observed properties of NGC 4555 confirm that elliptical galaxies can posses dark matter halos of their own, regardless of their environment," said O'Sullivan. "This raises an important question: what determines whether elliptical galaxies have dark matter halos?" Most large elliptical galaxies are found in groups and clusters of galaxies, and are likely the product of the merger of two spiral galaxies. In such an environment, the dark matter halos can be stripped away by gravitational tidal force and added to other galaxies or the group as a whole. Therefore, it is difficult to determine how much dark matter the original galaxies had, and how much they have lost to the group as a whole through interactions with their environment. The importance of the issue of the intrinsic amount of dark matter associated with an elliptical galaxy has recently increased owing to a report by an international team of astronomers led by Aaron Romanowsky of the University of Nottingham, United Kingdom. This team found little, if any evidence of dark matter in three elliptical galaxies. Two of these were in loose galaxy groups, and one was isolated. Their result, based on optical data from the 4.2 meter William Herschel Telescope on the Spanish island of La Palma, is in clear conflict with the X-ray data on NGC 4555. The optical technique used to search for dark matter in the nearby elliptical galaxies could not be applied to NGC 4555 because it is more than 3 times as far away from Earth. Either the galaxies observed by Romanowsky and colleagues have lost their dark matter halos through earlier interactions with other galaxies, or their dark matter halos are much more extended, or they formed without dark matter halos. The first option is possible for the galaxies in groups, but very unlikely for the isolated galaxy. The second and third options are still open, but would require a modification ˆ perhaps a major modification ˆ of the cold dark matter theory of galaxy formation. "This is clearly a question which deserves further consideration," said O'Sullivan. "It seems likely that much more theoretical and observational work on elliptical galaxies will be required before this issue can be resolved." Chandra observed NGC 4555 with its Advanced CCD Imaging Spectrometer (ACIS) in February 2003. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Office of Space Science, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov http://www.spaceref.com/news/viewpr.html?pid=15366

Dark Matter Halo Puzzles Astronomers Summary - (Oct 26, 2004) Astronomers using the Chandra X-Ray Observatory have discovered a huge halo of dark matter around an isolated elliptical galaxy; an object that shouldn't have such a halo, according to optical observations. The galaxy, NGC 4555, is unusual that it's a large elliptical galaxy which isn't part of a larger cluster of galaxies. It's surrounded by a cloud of gas, twice the size of the galaxy itself, that's been heated to 10-million-degrees Celsius. This gas could only get that hot if it was being constrained by a halo of dark matter ten times the mass of the stars in the galaxy. Full Story - Dark matter continues to confound astronomers, as NASA's Chandra X-ray Observatory demonstrated with the detection of an extensive envelope of dark matter around an isolated elliptical galaxy. This discovery conflicts with optical data that suggest a dearth of dark matter around similar galaxies, and raises questions about how galaxies acquire and keep such dark matter halos. The observed galaxy, known as NGC 4555, is unusual in that it is a fairly large, elliptical galaxy that is not part of a group or cluster of galaxies. In a paper to be published in the November 1, 2004 issue of the Monthly Notices of the Royal Astronomical Society, Ewan O'Sullivan of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA and Trevor Ponman of the University of Birmingham, United Kingdom, use the Chandra data to show that the galaxy is embedded in a cloud of 10-million-degree-Celsius gas. This hot gas cloud has a diameter of about 400,000 light years, about twice that of the visible galaxy. An enormous envelope, or halo, of dark matter is needed to confine the hot cloud to the galaxy. The total mass of the dark matter halo is about ten times the combined mass of the stars in the galaxy, and 300 times the mass of the hot gas cloud. A growing body of evidence indicates that dark matter - which interacts with itself and "normal" matter only through gravity - is the dominant form of matter in the universe. According to the popular "cold dark matter" theory, dark matter consists of mysterious particles left over from the dense early universe that were moving slowly when galaxies and galaxy clusters began to form. "The observed properties of NGC 4555 confirm that elliptical galaxies can posses dark matter halos of their own, regardless of their environment," said O'Sullivan. "This raises an important question: what determines whether elliptical galaxies have dark matter halos?" Most large elliptical galaxies are found in groups and clusters of galaxies, and are likely the product of the merger of two spiral galaxies. In such an environment, the dark matter halos can be stripped away by gravitational tidal force and added to other galaxies or the group as a whole. Therefore, it is difficult to determine how much dark matter the original galaxies had, and how much they have lost to the group as a whole through interactions with their environment. The importance of the issue of the intrinsic amount of dark matter associated with an elliptical galaxy has recently increased owing to a report by an international team of astronomers led by Aaron Romanowsky of the University of Nottingham, United Kingdom. This team found little, if any evidence of dark matter in three relatively nearby elliptical galaxies. Two of these were in loose galaxy groups, and one was isolated. Their result, based on optical data from the 4.2 meter William Herschel Telescope on the Spanish island of La Palma, is in clear conflict with the X-ray data on NGC 4555. The optical technique used to search for dark matter in the nearby elliptical galaxies could not be applied to NGC 4555 because it is more than 3 times as far away from Earth. Either the galaxies observed by Romanowsky and colleagues have lost their dark matter halos through earlier interactions with other galaxies, or their dark matter halos are much more extended, or they formed without dark matter halos. The first option is possible for the galaxies in groups, but very unlikely for the isolated galaxy. The second and third options are still open, but would require a modification - perhaps a major modification - of the cold dark matter theory of galaxy formation. "This is clearly a question which deserves further consideration," said O'Sullivan. "It seems likely that much more theoretical and observational work on elliptical galaxies will be required before this issue can be resolved." Chandra observed NGC 4555 with its Advanced CCD Imaging Spectrometer (ACIS) in February 2003. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Office of Space Science, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov Original Source: Chandra News Release http://www.universetoday.com/am/publish/dark_matter_halo_puzzles.html?26102004

11/02 23:43 "Lo más incomprensible es que el mundo sea comprensible" (Albert Einstein) Home > CIENCIA El Big Bang ocurre todos los días en el Universo Una nueva teoría cosmológica considera que la entropía es infinita El Big Bang no ha sido un episodio insólito en la historia del Universo, sino que constituye un fenómeno corriente, que se genera constantemente, creando múltiples universos paralelos en regiones remotas del espacio y del tiempo, según dos físicos de la Universidad de Chicago. Este modelo se basa en la naturaleza del vacío cuántico, lugar de procedencia del Universo, en el que la combinación de un pequeño vacío con una modesta inflación es suficiente para provocar entropía y crear universos. Este proceso de inflación universal es el que explica la flecha del tiempo. Por Eduardo Martínez. Siempre se nos ha enseñado que toda la creación se originó por una gran explosión cósmica, conocida como Big Bang, que ocurrió de forma excepcional y única en la historia del Universo hace unos 13 mil o 14 mil millones de años. Según el modelo del Big Bang, el Universo es finito y tuvo un comienzo en el momento en el que la materia existente alcanzó una densidad y una temperatura suficientemente alta para generar la explosión creativa. Los datos obtenidos hasta ahora por la observación directa coinciden con la teoría del Big Bang. Las primeras estrellas se formaron alrededor de mil millones de años después del Bing Bang. Pero nuestro Universo comenzará a contraerse en algún momento y aumentará su temperatura hasta llegar nuevamente a su estado inicial (Big Crunch). Sin embargo, una nueva teoría establece que el Big Bang podría no ser un fenómeno extraordinario, que la entropía es infinita y que el creciente desorden del Universo no conduce a la muerte cósmica, sino que prolonga la existencia de galaxias, estrellas y planetas hasta el infinito porque la flecha del tiempo, tal como la conocemos, ha podido tener otras direcciones en un pasado remoto inaccesible desde nuestra época. Big Bang diario Según esta teoría, el Big Bang es un acontecimiento cotidiano en la historia del Universo que sucede eternamente a escalas de tiempo increíblemente grandes, creando universos paralelos al nuestro en remotas regiones espaciotemporales porque la entropía no es finita, como se piensa actualmente, sino que en realidad es infinita. Es lo que proponen dos físicos de la Universidad de Chicago, Sean Carroll y Jennifer Chen, en un artículo en el que responden a dos de las cuestiones teóricas no resueltas por la física: por qué el flujo del tiempo transcurre únicamente en una dirección (del pasado al futuro), y por qué el Big Bang pudo ser realmente el resultado de una fluctuación de la energía procedente del vacío cuántico. La respuesta a ambas preguntas señala que la inflación universal es la que explica la flecha del tiempo, lo que no excluye que en un remoto pasado el tiempo pudiera tener una dirección inversa a los ojos de los astrónomos actuales. El Big Bang, a su vez, pudo formarse de la nada porque el vacío es el estado natural por excelencia, según la termodinámica, y porque basta la combinación de un pequeño vacío con una modesta inflación para provocar entropía y crear universos. La inflación es una prolongación de la teoría del Big Bang según la cual el Universo pasó por un período de expansión máxima en una fracción de segundo después del Big Bang. De ambas hipótesis se desprende que, posiblemente, ha habido múltiples explosiones similares al Big Bang que han podido crear universos paralelos al nuestro en regiones remotas del cosmos, tanto en el espacio como en el tiempo. La flecha del tiempo Tal como explica al respecto la Universidad de Chicago en un comunicado que ha traducido Astroseti, la cuestión sobre la flecha del tiempo intriga a los científicos porque la mayor parte de las leyes fundamentales de la física no separan el pasado del futuro. El concepto de entropía, a su vez, se basa en el flujo del tiempo, ya que establece que el desorden o caos aumenta con el paso del tiempo, tal como señaló el físico Ludwig Boltzmann hace ya un siglo. Espacio y tiempo son conceptos que no tienen sentido antes de la aparición de la materia en el Universo, por lo que en el modelo cosmológico actual se considera que el espacio y el tiempo aparecen con la materia en el mismo momento del Big-Bang. Según este modelo cosmológico, a medida que el tiempo fluye, la entropía global del Universo también aumenta. Como la flecha del flujo del tiempo es irreversible, la flecha de flujo de la entropía también es irreversible. En el Universo, la cantidad de energía útil disminuye paulatinamente y aumenta la forma degradada de energía. Dado que la entropía global siempre está en constante aumento, causará en algún momento el desplome térmico de todos los biosistemas en el Universo conocido, fenómeno conocido como Muerte Térmica del Biocosmos. Fin del Universo, de la vida, del tiempo y también de la entropía, según el actual modelo cosmológico. Entropía infinita Sin embargo, aunque el Universo posee una cantidad extrema de entropía específica que es esencial para la vida, continúa siendo un misterio descubrir por qué la entropía era escasa en los comienzos del Universo, una cuestión a la que los físicos de Chicago aportan ahora una singular respuesta. Lo que proponen es considerar que la entropía del Universo es infinita y no limitada en el tiempo, como se considera hasta ahora. De hecho, según su teoría, la entropía podría aumentar constantemente y evitar la muerte térmica del biocosmos. Carroll y Chen consideran que si la entropía es infinita, el Universo se expande eternamente gracias a la así conocida como energía oscura, que es la que está provocando que el Universo esté creciendo a un ritmo acelerado, en lugar de estar en desaceleración constante, tal como se ha verificado recientemente. Eso significa que en la actualidad la entropía continúa creciendo, lo que mantiene la expansión del Universo y al mismo tiempo lo llena de energía oscura, que es a nuestros ojos espacio vacío. La mayor parte de la energía observada en el Universo es del tipo de energía del vacío o energía oscura. Potencialidad del vacío cuántico Pero ese espacio vacío no es equivalente a la nada, toda vez que mantiene rastros débiles de energía a escala subatómica, tal como sugirieron, en un interesante artículo, Jaume Garriga, de la Universidad Autónoma de Barcelona, y Alexander Vilenkin, de la Universidad Tufts. Ambos consideran que las fluctuaciones del vacío cuántico pueden generar sus propios Bigs Bangs en diferentes áreas del Universo separadas entre sí tanto en el tiempo como en el espacio. En consecuencia, sostienen que debe haber un infinito número de regiones del espacio similares a la de nuestro Universo observable en las que posiblemente haya vida inteligente. Carroll y Chen amplían esta reflexión y sugieren que la expansión del Universo pudo iniciarse “al revés” en un pasado remoto: en el escenario que imaginan de las condiciones iniciales del Universo, ambos autores señalan que los acontecimientos pudieron ocurrir tanto hacia el pasado como hacia el futuro. Esta hipótesis implica que el tiempo pudo tener una dirección inversa a los ojos de los astrónomos actuales, respecto a la tradicional dirección del tiempo. Según razonan ambos autores, los universos creados en estas explosiones cósmicas no tienen en cuenta la dirección del tiempo y contribuyen a aumentar la entropía, lo que supone aceptar que el Universo nunca alcanza el equilibrio: si lo alcanzara la flecha del tiempo no existiría. La propuesta de Carroll y Chen revoluciona la tradicional teoría cosmológica, basada en la entropía finita. La entropía es el segundo principio de la termodinámica, que puede definirse esquemáticamente como el “progreso para la destrucción” o “desorden inherente a un sistema”. La Segunda Ley de la Termodinámica es la más universal de las leyes físicas. En su interpretación más general establece que a cada instante el Universo se hace más desordenado. Hay un deterioro general pero inexorable hacia el caos. Carroll y Chen añaden ahora que ese desorden no conduce a la muerte del Universo, sino a su expansión infinita. Eduardo Martínez 01/11/2004 Artículo leído 1459 veces Portada/Inicio Enviar a un amigo Versión para imprimir Ver 1 comentarios Otros artículos de esta misma sección El Big Bang ocurre todos los días en el Universo - 01/11/2004 El cáncer sigue las reglas del caos - 24/10/2004 Descubren cómo se puede vivir sin oxígeno - 17/10/2004 Descubren en Egipto el mayor campo de cráteres de meteoritos del mundo - 10/10/2004 La robótica revoluciona, por fin, el campo - 03/10/2004 Se precipita el retroceso de los glaciares andinos - 26/09/2004 Una nueva investigación establece que es posible vivir sin los sueños - 19/09/2004 Posible primera foto de un planeta exterior a nuestro sistema solar - 11/09/2004 La nanotecnología puede mejorar hasta 100 veces la actual velocidad de Internet - 05/09/2004 La primera comunicación láser entre Marte y la Tierra se probará en 2010 - 28/08/2004 [1]>> ©TENDENCIAS CIENTÍFICAS 2004 Mapa del sitio | Sindicación http://www.tendencias21.net/index.php?action=article&id_article=87823

Spitzer Finds New Globular Cluster Nearby Summary - (Oct 13, 2004) NASA's Spitzer Space Telescope has turned up a relatively close globular star cluster that was obscured by dust and invisible to most instruments. Andrew Monson from the University of Wyoming first discovered the cluster while scanning for objects in the dusty mid-plane of the Milky Way. Follow up observations determined that the cluster is only 9,000 light-years away from the Earth in the constellation of Aquila, making it one of the closest clusters to our planet. Full Story - Just when astronomers thought they might have dug up the last of our galaxy's "fossils," they've discovered a new one in the galactic equivalent of our own backyard. Called globular clusters, these ancient bundles of stars date back to the birth of our Milky Way galaxy, 13 or so billion years ago. They are sprinkled around the center of the galaxy like seeds in a pumpkin. Astronomers use clusters as tools for studying the Milky Way's age and formation. New infrared images from NASA's Spitzer Space Telescope and the University of Wyoming Infrared Observatory reveal a never-before-seen globular cluster within the dusty confines of the Milky Way. The findings will be reported in an upcoming issue of the Astronomical Journal. "It's like finding a long-lost cousin," said Dr. Chip Kobulnicky, a professor of physics and astronomy at the University of Wyoming, Laramie, and lead author of the report. "We thought all the galaxy's globular clusters had already been found." "I couldn't believe what I was seeing," said Andrew Monson, a graduate student at the University of Wyoming, who first spotted the cluster. "I certainly wasn't expecting to find such a cluster." The newfound cluster is one of about 150 known to orbit the center of the Milky Way. These tightly packed knots of stars are among the oldest objects in our galaxy, having formed about 10 to 13 billion years ago. They contain several hundred thousand stars, most of which are older and less massive than our Sun. Monson first noticed the cluster while scanning data from the Spitzer Space Telescope's Galactic Legacy Infrared Mid-Plane Survey Extraordinaire - a survey to find objects hidden within the dusty mid-plane of our galaxy. He then searched archival data for a match and found only one undocumented image of the cluster from a previous NASA-funded infrared survey of the sky, called the Two Micron All-Sky Survey. "The cluster was there in the data but nobody had found it," said Monson. "This discovery demonstrates why Spitzer is so powerful - it can see objects that are completely hidden in visible light," said Dr. Michael Werner of NASA's Jet Propulsion Laboratory, Pasadena, Calif., project scientist for Spitzer. "This is particularly relevant to the study of the plane of our galaxy, where dust blocks most visible light." Follow-up observations with the University of Wyoming Infrared Observatory helped set the distance of the new cluster at about 9,000 light-years from Earth - closer than most clusters -- and set the mass at the equivalent of 300,000 Suns. The cluster's apparent size, as viewed from Earth, is comparable to a grain of rice held at arm's length. It is located in the constellation Aquila. The research team consists of astronomers from the University of Wisconsin, Madison; Boston University, Boston, Mass.; the University of Maryland, College Park, Md.; the University of Minnesota, Twin Cities; the Space Science Institute, Boulder, Colo.; and the Spitzer Science Center, Pasadena, Calif. The Galactic Legacy Infrared Mid-Plane Survey Extraordinaire is managed by the University of Wisconsin and led by Dr. Ed Churchwell. JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington, D.C. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. JPL is a division of Caltech. Spitzer's infrared array camera, which captured the new cluster, was built by NASA Goddard Space Flight Center, Greenbelt, Md. The camera's development was led by Dr. Giovanni Fazio of Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. http://www.universetoday.com/am/publish/spitzer_new_globular_cluster_nearby.html?13102004

Un equipo de astrónomos halla un objeto desconocido con un campo magnético superior al Sol Es demasiado grande para ser un planeta y demasiado pequeño para ser una estrella ¿Por qué consumer.es incluye publicidad? A través de los telescopios Gemini North y Keck II, un equipo de científicos ha hallado un objeto "misterioso", que se encuentra a 300 años luz de la Tierra, que tiene un campo magnético que es 14 millones de veces superior al del Sol. En un principio pensaron que se trataba de una estrella con un tamaño similar al del Sol, que podría haber ido perdiendo su masa al interactuar con otra estrella próxima, según se publicará en la revista "Astrophysical Journal". Por su parte uno de los miembros del equipo de astrónomos, Thomas E. Harrison, ha declarado que es un objeto "demasiado grande" como para considerarlo un superplaneta aunque tampoco es lo suficientemente grande como para que se considere una estrella por lo que resulta "imposible" encuadrarlo en ninguna categoría. En un principio los indicios apuntaban a que el objeto podría ser una estrella que ha ido perdiendo parte de su masa al interactuar con su estrella vecina hasta llegar a convertirse en un objeto enano y que entre ellas se produjo un proceso de transferencia de masa con explosiones. Harrison explica que este hecho puede ser el que ocasionó el acercamiento de sus órbitas hasta el punto de que, en la actualidad, la distancia que las separa es similar a la existente entre la Tierra y la Luna, aunque aun quedarían por descubrir las causas que causaron el inicio de este proceso de transferencia de masa constituyen una incógnita. Por todo ello creen que se trata de un sistema de estrellas binario formado por una estrella con el 60% de masa solar y un objeto estelar enano con un volumen de "sólo" 1/20.000 de masa solar y que aun puede emitir "grandes cantidades" de luz, según Harrison. http://www.consumer.es/web/es/noticias/educacion_y_ciencia/2004/10/08/110068.php

Descubren proceso de formación de planetas Agencias Un equipo de astrónomos que opera el telescopio espacial Spitzer de la NASA, dio a conocer el proceso por el cual se forman los planetas, al estudiar nubes de gas y polvo alrededor de estrellas con sistemas planetarios en gestación. El descubrimiento se logró gracias a la sensibilidad de Spitzer en el infrarrojo, lo que permitió a los astrónomos observar el interior de las mismas. Ellos descubrieron que los planetas se forman por la colisión de grandes fragmentos de rocas del tamaño de montañas en grandes nubes de polvo. El trabajo publicado en la revista Astrophysical Journal, revela por primera vez el proceso de formación embrionaria de cuerpos como la Tierra y Marte, el que de acuerdo a los astrónomos es mucho menos caótico de lo que se pensaba. Los resultados se lograron luego de estudiar el interior de las nubes con los instrumentos infrarrojos ultrasensibles del telescopio Spitzer en alrededor de 266 estrellas cercanas de tamaño similar y hasta 3 veces la masa del Sol. Spitzer ofreció así un panorama más amplio de cómo los planetas pueden formarse más allá de la visión tradicional que prevalecía hasta hoy, en la que se pensaba que los cuerpos protoplanetarios acumulaban como una bola de nieve masa del polvo dentro de una nebulosa, hasta llegar a una etapa más violenta y caótica donde colisiones de gran tamaño señalaban el último periodo de formación planetaria. Spitzer ha mostrado a los astrónomos nuevas posibilidades en la formación de los planetas. http://www.elsiglodedurango.com.mx/start/nID/32614/

No Sunspots at All Summary - (Oct 18, 2004) On October 11, solar astronomers saw something they haven't seen on the Sun in six years... nothing. Not a single sunspot. Within a couple of days, of course, a sunspot popped up, and they're on the Sun right now. This is a clear indication to astronomers that the Sun is on its way to the low point of its 11-year cycle of activity, called the "solar minimum". During the solar minimum, the Sun can be without spots for days or even weeks, and solar flares subside. Astronauts will breath a sigh of relief; it's a safer time to be out in space. Full Story - Six … long … years. Solar physicist David Hathaway has been checking the sun every day since 1998, and every day for six years there have been sunspots. Sunspots are planet-sized "islands" on the surface of the sun. They are dark, cool, powerfully magnetized, and fleeting: a typical sunspot lasts only a few days or weeks before it breaks up. As soon as one disappears, however, another emerges to take its place. Even during the lowest ebb of solar activity, you can usually find one or two spots on the sun. But when Hathaway looked on Jan. 28, 2004, there were none. The sun was utterly blank. It happened again last week, twice, on Oct. 11th and 12th. There were no sunspots. "This is a sign," says Hathaway, "that the solar minimum is coming, and it's coming sooner than we expected." Solar minimum and solar maximum--"Solar Min" and "Solar Max" for short--are two extremes of the sun's 11-year activity cycle. At maximum, the sun is peppered with spots, solar flares erupt, and the sun hurls billion-ton clouds of electrified gas toward Earth. It's a good time for sky watchers who enjoy auroras, but not so good for astronauts who have to be wary of radiation storms. Power outages, zapped satellites, malfunctioning GPS receivers--these are just a few of the things that can happen during Solar Max. Solar minimum is different. Sunspots are fewer--sometimes days or weeks go by without a spot. Solar flares subside. It's a safer time to travel through space, and a less interesting time to watch polar skies. Hathaway is an expert forecaster of the solar cycle. He keeps track of sunspot numbers (the best known indicator of solar activity) and predicts years in advance when the next peaks and valleys will come. It's not easy: "Contrary to popular belief," says Hathaway, "the solar cycle is not precisely 11 years long." Its length, measured from minimum to minimum, varies: "The shortest cycles are 9 years, and the longest ones are about 14 years." What makes a cycle long or short? Researchers aren't sure. "We won't even know if the current cycle is long or short--until it's over," he says. But researchers are making progress. Hathaway and colleague Bob Wilson, both working at NASA's Marshall Space Flight Center, believe they've found a simple way to predict the date of the next solar minimum. "We examined data from the last 8 solar cycles and discovered that Solar Min follows the first spotless day after Solar Max by 34 months," explains Hathaway. The most recent solar maximum was in late 2000. The first spotless day after that was Jan 28, 2004. So, using Hathaway and Wilson's simple rule, solar minimum should arrive in late 2006. That's about a year earlier than previously thought. The next solar maximum might come early, too, says Hathaway. "Solar activity intensifies rapidly after solar minimum. In recent cycles, Solar Max has followed Solar Min by just 4 years." Do the math: 2006 + 4 years = 2010. By that time, according to NASA's new vision for space exploration, robot ships will be heading for the moon in advance of human explorers. If Hathaway and Wilson's prediction is correct, those robots will need good shields. Solar flares and radiation storms can damage silicon brains and electronic guts almost as badly as their organic counterparts. For now, says Hathaway, we're about to experience "the calm before the storm." And although he's a fan of solar activity--what solar physicist isn't?--he's looking forward to the lull. "It'll give us a chance to see if our 'spotless sun' method for predicting solar minimum really works." Solar Max will be back soon enough. Original Source: Science@NASA Story http://www.universetoday.com/am/publish/no_sunspots_at_all.html?18102004

Early Solar System Was a Mess Summary - (Oct 19, 2004) Brand new planetary systems take much longer to form than previously thought, according to new data gathered by the Spitzer Space Telescope - and it's a nasty, chaotic period. Researchers pointed Spitzer at 71 dusty disks which are new planets in the making, and found that many seem choked with dust, hundreds of millions of years after the host star formed. The only way this could be possible is if mountain range-sized planetesimals were continuously crashing into each other on the long hard road to full sized planethood. Full Story - Planets are built over a long period of massive collisions between rocky bodies as big as mountain ranges, astronomers announced today. New observations from NASA's Spitzer Space Telescope reveal surprisingly large dust clouds around several stars. These clouds most likely flared up when rocky, embryonic planets smashed together. The Earth's own Moon may have formed from such a catastrophe. Prior to these new results, astronomers thought planets were formed under less chaotic circumstances. "It's a mess out there," said Dr. George Rieke of the University of Arizona, Tucson, first author of the findings and a Spitzer scientist. "We are seeing that planets have a long, rocky road to go down before they become full grown." Spitzer was able to see the dusty aftermaths of these collisions with its powerful infrared vision. When embryonic planets, the rocky cores of planets like Earth and Mars, crash together, they are believed to either merge into a bigger planet or splinter into pieces. The dust generated by these events is warmed by the host star and glows in the infrared, where Spitzer can see it. The findings will be published in an upcoming issue of the Astrophysical Journal. They mirror what we know about the formation of our own planetary system. Recent observations from studies of our Moon's impact craters also reveal a turbulent early solar system. "Our Moon took a lot of violent hits when planets had already begun to take shape," Rieke said. According to the most popular theory, rocky planets form somewhat like snowmen. They start out around young stars as tiny balls in a disc-shaped field of thick dust. Then, through sticky interactions with other dust grains, they gradually accumulate more mass. Eventually, mountain-sized bodies take shape, which further collide to make planets. Previously, astronomers envisioned this process proceeding smoothly toward a mature planetary system over a few million to a few tens of millions of years. Dusty planet-forming discs, they predicted, should steadily fade away with age, with occasional flare-ups from collisions between leftover rocky bodies. Rieke and his colleagues have observed a more varied planet-forming environment. They used new Spitzer data, together with previous data from the joint NASA, United Kingdom and the Netherlands' Infrared Astronomical Satellite and the European Space Agency's Infrared Space Observatory. They looked for dusty discs around 266 nearby stars of similar size, about two to three times the mass of the Sun, and various ages. Seventy-one of those stars were found to harbor discs, presumably containing planets at different stages of development. But, instead of seeing the discs disappear in older stars, the astronomers observed the opposite in some cases. "We thought young stars, about one million years old, would have larger, brighter discs, and older stars from 10 to 100 million years old would have fainter ones," Rieke said. "But we found some young stars missing discs and some old stars with massive discs." This variability implies planet-forming discs can become choked with dust throughout the discs' lifetime, up to hundreds of millions of years after the host star was formed. "The only way to produce as much dust as we are seeing in these older stars is through huge collisions," Rieke said. Before Spitzer, only a few dozen planet-forming discs had been observed around stars older than a few million years. Spitzer's uniquely sensitive infrared vision allows it to sense the dim heat from thousands of discs of various ages. "Spitzer has opened a new door to the study of discs and planetary evolution," said Dr. Michael Werner, project scientist for Spitzer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "These exciting new findings give us new insights into the process of planetary formation, a process that led to the birth of planet Earth and to life," said Dr. Anne Kinney, director of the universe division in the Science Mission Directorate at NASA Headquarters, Washington. "Spitzer truly embodies NASA's mission to explore the universe and search for life," she said. JPL manages the Spitzer Space Telescope for NASA's Science Mission Directorate. Artist's concepts and additional information about the Spitzer Space Telescope is available at http://www.spitzer.caltech.edu. Original Source: NASA/JPL News Release http://www.universetoday.com/am/publish/early_solar_system_was_mess.html?19102004

Últimas noticias sobre el Ciclo Solar Algo extraño ha pasado en el Sol esta última semana: todas las manchas solares han desaparecido. Esto es una señal, dicen los científicos, de que el mínimo solar está más cerca de lo que se esperaba. Octubre 18, 2004: Seis... largos... años. El físico solar David Hathaway ha estado observando el Sol todos los días desde 1998, y cada día, desde hace seis años ha encontrado manchas solares. Las manchas solares son "islas" del tamaño de planetas, que aparecen en la superficie del Sol. Son oscuras, frías, extremadamente magnetizadas y efímeras ya que una mancha solar sólo dura unos pocos días o semanas antes de desaparecer. Tan pronto como una de ellas desaparece, otra emerge y toma su lugar. Incluso durante la etapa de actividad mínima solar, se pueden ver una o dos manchas solares. Pero cuando Hathaway miró el 28 de Enero de 2004, allá no había nada. El Sol estaba completamente limpio. Y esto mismo volvió a ocurrir la última semana, dos veces, el 11 y 12 de Octubre. No había ni rastro de manchas solares. "Esto es una señal" dice Hathaway, "de que el mínimo solar está próximo, y más cerca de lo que pensábamos". Derecha: El Sol sin manchas, el 11 de octubre de 2004, fotografiado por el Observatorio Solar y Heliosférico de la ESA/NASA. Mínimo solar y máximo solar -- "Solar Min" y "Solar Max" para abreviar -- son los dos extremos del ciclo de 11 años de actividad solar. En el máximo, el Sol se encuentra salpicado con manchas, llamaradas, y arroja miles de millones de toneladas de nubes y gas electrificado hacia la Tierra. Es un buen momento para los observadores del cielo que disfrutan entonces con la visión de las auroras, pero no tan bueno para los astronautas que deben tener cuidado con las tormentas radioactivas. Fluctuaciones en la potencia eléctrica, satélites inutilizados, defectos en el funcionamiento de los dispositivos del GPS -- son unos pocos ejemplos de lo que puede pasar durante el máximo de actividad solar. Anótese aquí para recibir nuestro servicio de ENTREGA INMEDIATA DE NOTICIAS CIENTÍFICAS El mínimo solar es diferente. Las manchas solares son pocas -- a veces pueden pasar días o semanas sin una mancha. Las llamaradas solares amainan. Es un buen momento para viajar por el espacio, pero es menos interesante para observar los cielos polares. Hathaway es un experto en predicciones del ciclo solar. Observa el número de manchas (el mejor indicador conocido de la actividad solar) y predice con años de anticipación cuando aparecerán los próximos picos y valles. No es una tarea fácil. "A pesar de la creencia popular", dice Hathaway, "el ciclo solar no es exactamente de 11 años". Su longitud, medida desde el mínimo hasta el máximo, varía: "El ciclo más corto puede ser de 9 años, y el ciclo más largo de 14". ¿Qué determina que un ciclo sea corto o largo? Los investigadores no están seguros. "Ni siquiera sabemos si un ciclo es corto o largo hasta que ha terminado", dicen. Arriba: Los astrónomos han contado manchas solares por cientos de años. Esta gráfica muestra el número de manchas solares desde 1610 hasta 2000. Para ver los datos del ciclo actual (1996-2000) haga clic aquí. Los investigadores, sin embargo, están progresando. Hathaway y su colega Wilson, ambos trabajando en el Centro Marshall de Vuelos Espaciales de la NASA, creen que han encontrado una regla muy simple para predecir la fecha del próximo mínimo solar. "Examinamos la información de los ocho últimos ciclos solares y descubrimos que el "Solar Min" sigue al primer día sin manchas que aparece después del "Solar Max" en 34 meses", explica Hathaway. El último máximo del ciclo solar fue a finales de 2000. El primer día sin manchas después de éste fue el 28 de Enero de 2004. De este modo, usando la regla de Hathaway y Wilson, el mínimo solar aparecerá a finales de 2006. Esto es aproximadamente un año antes de lo previsto. El próximo máximo solar puede también ocurrir muy pronto, dice Hathaway. "La actividad solar se intensifica rápidamente después del mínimo solar. En los últimos ciclos, el Solar Max ha seguido al Solar Min justo después de 4 años". Aplicando las matemáticas: 2006 + 4 años = 2010. Según las nuevas perspectivas para la exploración espacial de la NASA, naves robot iniciarán una expedición a la luna como avanzada de los exploradores humanos. Si la predicción de Hathaway y Wilson es correcta, estos robots necesitarán unos buenos escudos protectores. Las llamaradas solares y las tormentas radioctivas pueden dañar los cerebros de silicio y los circuitos electrónicos al menos tanto como a sus homólogos humanos. Derecha: Recreación artística de una nave espacial robot. Autor: Pat Rawlings. [Más información] Por el momento, dice Hathaway, estamos experimentando "la calma que precede a la tormenta". Y aunque es un fanático de la actividad solar -- ¿qué físico no lo es? -- está esperando con impaciencia la calma. "Nos dará una oportunidad para comprobar si nuestro método, "Sol limpísimo" para predecir el mínimo, funciona realmente". Después, el máximo solar regresará también en su momento. http://ciencia.msfc.nasa.gov/headlines/y2004/18oct_solarminimum.htm?list1176985

The Chandra image of NGC 4555 revealed that this large, isolated, elliptical galaxy is embedded in a cloud of 10-million-degree Celsius gas (left). The hot gas cloud has a diameter of about 400,000 light years, roughly twice that of the visible galaxy (right). X-ray/Optical Composite of NGC 4555 Astronomers have concluded that the combined gravity of the stars in the galaxy is far too low to hold the hot gas cloud to the galaxy - an enormous envelope, or halo, of dark matter is needed. The total mass of the required dark matter halo is about ten times the combined mass of the stars in the galaxy, and 300 times the mass of the hot gas cloud. Dissolve from Optical to X-ray View of NGC 4555 A growing body of evidence indicates that dark matter - which interacts with itself and normal matter only through gravity - is the dominant form of matter in the universe. According to the popular "cold dark matter" theory, dark matter consists of mysterious particles left over from the dense early universe that were moving slowly when galaxies and galaxy clusters began to form. Most large, elliptical galaxies are found in groups and clusters of galaxies where they can gain or lose dark matter through collisions with other galaxies, so it is difficult to determine how much dark matter they originally possessed. The Chandra observation of NGC 4555 confirms that an isolated, elliptical galaxy can possess a dark matter halo of its own. http://chandra.harvard.edu/photo/2004/ngc4555/

Arizona Telescope Turned Into a Robot Summary - (Oct 20, 2004) Engineers have finished converting a telescope in Arizona into a robot. The Peters Automated Infrared Imaging Telescope (PAIRITEL), based at the Fred L. Whipple Observatory at Mt. Hopkins, Arizona will now be used to analyze gamma ray bursts (GRBs) and other short-lived events. PAIRITEL will receive alerts from NASA's Swift spacecraft, which will detect GRBs from any part of the sky. In under 2 minutes, it'll automatically be focused on the region where the GRB happened, and then start watching to see how events unfold after the explosion. This should give astronomers plenty of data to help understand what causes these enormous explosions. Full Story - Today, the world of astronomy meets the science fiction world of Isaac Asimov's "I, Robot" with the commissioning of a new robotic telescope. While it lacks the humanoid qualities of the movie version, this robot will aid in humanity's quest to understand the early universe by observing the most distant and powerful explosions known. Located at the Fred L. Whipple Observatory on Mt. Hopkins, Arizona, the Peters Automated Infrared Imaging Telescope (PAIRITEL) is the first fully "robotic" infrared telescope in North America dedicated to observing transient astronomical events. The telescope, used for several years in a major all-sky survey (2MASS), has been refurbished to work autonomously. It will operate in tandem with NASA's new gamma-ray burst satellite "Swift," to be launched on November 8 from Kennedy Space Center. With PAIRITEL, a team of astronomers led by Dr. Joshua Bloom of the Harvard Society of Fellows, Harvard-Smithsonian Center for Astrophysics (CfA) and UC Berkeley, hopes to pinpoint the gamma-ray burst explosions from the first and most distant stars in the universe. A gamma ray burst (GRB) is a quick flash of gamma-ray radiation lasting about a minute, accompanied by an afterglow emission of X-rays, visible, infrared, and radio light. The afterglow may be observable for days to weeks afterward. The majority of GRBs are believed to be due to massive stars that explode violently and release tremendous blasts of energy. "Innovatively exploring the night sky in the time domain - seeing how things change from night to night, and even from minute to minute - is the next big frontier in astronomy," said Bloom. "PAIRITEL was optimized to study cosmic events like GRBs that are here today and gone tomorrow." Peering back to a time when the universe was less than 1 billion years old is the holy grail of observational astronomy. So far, only energetic galaxy cores known as quasars have been used to probe the early universe. But gamma-ray burst afterglows, if astronomers are able to image them quickly, hold clear advantages over quasars. For up to one hour after the burst, afterglow brightnesses can reach up to 1000 times that of the brightest known quasar in the universe. Also, explained Bloom, "The stars that create GRBs likely formed before the black holes that create quasars. So by looking for the youngest and most distant GRBs, we can study the earliest epochs of the universe." A key feature of PAIRITEL that will allow the location of distant GRBs is its rapid response time. PAIRITEL will receive signals from Swift and automatically move, in under 2 minutes, to the part of the sky where a GRB has appeared. "My ultimate vision is to have astronomy robots talking to robots, deciding what to observe and how, with no human intervention," said Bloom. "As it is, PAIRITEL only e-mails us when it's found a particularly interesting source, or when something goes wrong and it needs help!" Another key feature of PAIRITEL is its sensitivity at infrared wavelengths, setting this system apart from the bevy of visible-light robotic telescopes already in existence. Images taken with infrared filters (about twice the wavelength of visible light) are indispensable: visible light emitted from more than 12 billion light-years away is completely extinguished for observers on Earth. Bloom explained, "Forget about the dimming due to the extreme distances: the hydrogen gas between us and the explosions makes it like searching for a firefly behind a thick London fog. In the infrared we can peer through the shroud to the good stuff." In addition, the unique camera on PAIRITEL takes pictures simultaneously at three different wavelengths of light, allowing for instantaneous full-color snapshots. The Swift spacecraft will find GRBs at a rate 10 to 20 times higher than currently feasible, and should find more bursts in 6 months than all well-studied bursts to date. Bloom said he is most excited about using Swift and PAIRITEL "together to find the golden needle in the haystack - a high-redshift GRB that's farther away than the most distant known galaxy or quasar." When PAIRITEL is not chasing down GRBs, it will be used to make precision measurements of supernovae to help determine the few fundamental parameters that dictate the expansion of the universe. Among other projects, Dr. Michael Pahre (CfA) will use PAIRITEL to study the near-infrared light of nearby galaxies to compare it with mid-infrared light in images obtained with NASA's Spitzer Space Telescope. Harvard graduate student Cullen Blake, who has written software for the project, will also use PAIRITEL to try to find Earth-mass planets around brown dwarfs. Other PAIRITEL team members include: Prof. Mike Skrutskie (Univ. of Virginia), Dr. Andrew Szentgyorgyi (CfA), Prof. Robert Kirshner (Harvard University/CfA), Dr. Emilio Falco (CfA), Dr. Thomas Matheson (NOAO), and Dan Starr (Gemini Observatory, Hawaii). The staff of Mt. Hopkins-Wayne Peters, Bob Hutchins, and Ted Groner-worked on the automation of the telescope. PAIRITEL, nearly 2 years after the inception of the project, is being dedicated today to the late Jim Peters, who worked for the Smithsonian Astrophysical Observatory, first on satellite tracking and then as a telescope operator on Mt. Hopkins for 25 years. His widow and son will be in attendance at the ceremony. The project was funded by a grant from the Harvard Milton Fund. The telescope is owned by the Smithsonian Astrophysical Observatory and the infrared camera is on loan from the University of Virginia. Additional information about Swift and PAIRITEL is available online at: http://swift.gsfc.nasa.gov/docs/swift/swiftsc.html http://pairitel.org/ Original Source: CfA News Release http://www.universetoday.com/am/publish/arizona_telescope_robot.html?20102004

Mystery Object in the Milky Way's Halo Summary - (Oct 20, 2004) The Milky Way is a messy eater. When it collides with other galaxies and consumes them, it leaves shredded collections of stars around called dwarf galaxies. Astronomers poring through the data from the Sloan Digital Sky Survey have found what they think could be a new dwarf galaxy. This new object, called Willman 1, is dim: 200 times less luminous than any other nearby dwarf galaxy. Further observations could validate the theory that the Milky Way is surrounded by clumps of dark matter, each of which has a dwarf galaxy in their centre. Full Story - Most of the stars in our Milky Way galaxy lie in a very flat, pinwheel-shaped disk. Although this disk is prominent in images of galaxies similar to the Milky Way, there is also a very diffuse spherical "halo" of stars surrounding and enclosing the disks of such galaxies. Recent discoveries have shown that this outer halo of the Milky Way is probably composed of small companion galaxies ripped to shreds as they orbited the Milky Way. A discovery announced today by the Sloan Digital Sky Survey (SDSS) reveals a clump of stars unlike any seen before. The findings may shed light on how the Milky Way's stellar halo formed. This clump of newly discovered stars, called SDSSJ1049+5103 or Willman 1, is so faint that it could only be found as a slight increase in the number of faint stars in a small region of the sky. "We discovered this object in a search for extremely dim companion galaxies to the Milky Way," explains Beth Willman of New York University's Center for Cosmology and Particle Physics. "However, it is 200 times less luminous than any galaxy previously seen." Another possibility, adds Michael Blanton, an SDSS colleague of Willman's at New York University, is that Willman 1 is an unusual type of globular cluster, a spherical agglomeration of thousands to millions of old stars." "Its properties are rather unusual for a globular cluster. It is dimmer than all but three known globular clusters. Moreover, these dim globular clusters are all much more compact than Willman 1", explains Blanton. "If it's a globular cluster, it is probably being torn to shreds by the gravitational tides of the Milky Way." The real distinction between the globular cluster and dwarf galaxy interpretations is that galaxies are usually accompanied by substantial quantities of dark matter, says Julianne Dalcanton, an SDSS researcher at the University of Washington. "Clearly the next step is to carry out additional measurements to determine whether there is any dark matter associated with Willman 1." SDSS consortium member Daniel Zucker of the Max Planck Institute for Astronomy in Heidelberg, Germany, says the Sloan Digital Sky Survey has proven to be "a veritable gold mine for studies of the outer parts of our galaxy and its neighbors, as shown by Dr. Willman's discovery, and by our group's earlier discovery of a giant stellar structure and a new satellite galaxy around the Andromeda Galaxy." If Willman 1 does turn out to be a dwarf galaxy, this discovery could shed light on a long-standing mystery. The prevailing 'Cold Dark Matter' model predicts that our own Milky Way galaxy is surrounded by hundreds of dark matter clumps, each a few hundred light years in size and possibly populated by a dwarf galaxy. However, only 11 dwarf galaxies have been discovered orbiting the Milky Way. Perhaps some of these clumps have very few embedded stars, making the galaxies particularly difficult to find. "If this new object is in fact a dwarf galaxy, it may be the tip of the iceberg of a yet unseen population of ultra-faint dwarf galaxies," suggests Willman. The Milky Way has been an area of intense research by SDSS consortium members. "The colors of the stars in Willman 1 are similar to those in the Sagittarius tidal stream, a former dwarf companion galaxy to the Milky Way now in the process of merging into the main body of our Galaxy," explains Brian Yanny, an SDSS astrophysicist at The Department of Energy's Fermi National Accelerator Laboratory, a leader in research on the Milky Way's accretion of material. Continues Yanny: "If Willman 1 is a globular cluster, then it may have piggybacked a ride into our Galaxy's neighborhood on one of these dwarf companions, like a tiny mite riding in on a flea as it, in turn, latches onto a massive dog." "Whether it is a globular cluster or a dwarf galaxy, this very faint object appears to represent one of the building blocks of the Milky Way," Willman said. Original Source: SDSS News Release http://www.universetoday.com/am/publish/mystery_object_milky_way_halo.html?20102004

Some Stars Take an Erratic Journey Summary - (Oct 20, 2004) Our Solar System takes a very consistent journey as it completes an orbit around the centre of the Milky Way galaxy, similar to the way our Earth goes around the Sun. But astronomers from the European Space Agency have used the Hipparcos space-based observatory to find stars which don't stay put in the galaxy. Instead, these rogue stars will travel on a more erratic path, perhaps given a kick by the denser leading edge of the Milky Way's spiral arms. These kinds of stars account for 20% of stars within 1000 light-years of the Sun, so it's a very common situation. Full Story - A team of European astronomers has discovered that many stars in the vicinity of the Sun have unusual motions caused by the spiral arms of our galaxy, the Milky Way. According to this research, based on data from ESA's Hipparcos observatory, our stellar neighbourhood is the crossroads of streams of stars coming from several directions. Some of the stars hosting planetary systems could be immigrants from more central regions of the Milky Way. The Sun and most stars near it follow an orderly, almost circular orbit around the centre of our galaxy, the Milky Way. Using data from ESA's Hipparcos satellite, a team of European astronomers has now discovered several groups of 'rebel' stars that move in peculiar directions, mostly towards the galactic centre or away from it, running like the spokes of a wheel. These rebels account for about 20% of the stars within 1000 light-years of the Sun, itself located about 25 000 light-years away from the centre of the Milky Way. The data show that rebels in the same group have little to do with each other. They have different ages so, according to scientists, they cannot have formed at the same time nor in the same place. Instead, they must have been forced together. "They resemble casual travel companions more than family members," said Dr Benoit Famaey, Université Libre de Bruxelles, Belgium. Famaey and his colleagues believe that the cause forcing the rebel stars together on their unusual trajectory is a 'kick' received from one of the Milky Way's spiral arms. The spiral arms are not solid structures but rather regions of higher density of gas and stars, called 'density waves' and similar to traffic hot-spots along the motorway. An approaching density wave compresses the gas it encounters and favours the birth of new stars, but it can also affect pre-existing stars by deflecting their motion. After the wave has passed, many stars will thus travel together in a stream, all in the same direction, even though they were originally on different trajectories or not even born. This research has shown that the neighbourhood of the Sun is a crossroads of many streams, made up of stars with different origins and chemical composition. These streams could also account for many of the stars with planetary systems recently discovered near the Sun. Astronomers know that stars with planetary systems preferentially form in dense gas clouds with a high metal content, such as those located in the more central regions of the Milky Way. The streams discovered by Hipparcos could be the mechanism that brought them closer to the Sun. As Famaey explains, "If these stars are kicked by a spiral arm, they can be displaced thousands of light-years away from their birthplace." These stars, together with their planets, can thus have migrated closer to the Sun. To learn more about the structure of our Milky Way, an aggregate of thousands of millions of stars, astronomers look at the way in which stars stay together in a coherent way or move with respect to the Sun and relative to one another. During its four-year mission, ESA's Hipparcos satellite has measured the distance and motion of more than a hundred thousand stars within a 1000 light-years of the Sun. However, while Hipparcos's data show in which directions stars are moving on the sky, they cannot tell whether stars are coming towards us or going away from us. By combining the Hipparcos data with ground-based measurements of their ‘Doppler shift’, obtained with a Swiss telescope at the Observatoire de Haute-Provence, France, Famaey and his colleagues could add the missing third dimension, namely the speed with which stars approach us or recede from us. Because of the Doppler shift, the colour of a star appears to change when it travels towards us or away from us, becoming respectively bluer or redder and giving astronomers information about its motion. "By combining all these first-class data, we now have a comprehensive, three-dimensional view of how nearby stars move about us," said Famaey. Scientists now wonder how widespread are the streams discovered by Famaey's team and what role they could play in the evolution of our galaxy. "This result opens up exciting new prospects for our understanding of the dynamics of the Milky Way," said Dr Michael Perryman, ESA Hipparcos and Gaia project scientist. ESA's forthcoming mission Gaia, scheduled for launch in 2011, will make it possible to extend this investigation over a much wider region of our galaxy. Gaia will observe more than a thousand million stars and will measure their motion in all three dimensions simultaneously, thanks to the on-board spectrograph providing information on their Doppler shift. "This will give us the clearest view ever of the structure and evolution of the Milky Way," Perryman said. Original Source: ESA News Release http://www.universetoday.com/am/publish/stars_travel_up_and_down_galaxy.html?20102004

Detecta la NASA otros 61 planetas en diversas etapas de desarrollo ( Redacción ) ( 2004-10-20 ) Recomienda esta nota Versión para imprimir Opina sobre el tema Astrónomos de la NASA revelaron ayer que los planetas se construyen con base en un período largo de colisiones masivas entre los cuerpos rocosos, tan grandes como las montañas. Las nuevas observaciones del telescopio espacial Spitzer revelan que las nubes de polvo son asombrosamente grandes y se ubican alrededor de varias estrellas. Estas nubes, revelaron los científicos estadunidenses, reciben una gama de luces cuando hay cuerpos rocosos, en medio de planetas que están a punto de formarse. Los expertos de la NASA buscaron formaciones polvorientas alrededor de 266 estrellas de tamaño similar y de distintas edades. Setenta y uno de esas estrellas fueron detectadas con enormes posibilidades de contener nuevos planetas en diversas etapas del desarrollo. Los planetas que tienen luna, pudieron haberse formado de una catástrofe similar. Antes de conocer estos resultados, los astrónomos pensaban que los planetas se formaban bajo circunstancias menos caóticas. George Rieke de la Universidad del Arizona, fue uno de los primeros investigadores que realizaron las observaciones, “hoy sabemos que los planetas tienen un camino largo para su formación, en medio de rocas y colisiones”. “Mediante el telescopio Spitzer es posible observar por medio de su visión infrarroja de gran alcance los resultados de estas colisiones”. Es factible que planetas como la Tierra y Marte se hallan formado de la fusión con un planeta mayor, explicó el investigador de la NASA. El polvo generado por estos acontecimientos es calentado por el Sol y brilla intensamente en el infrarrojo, donde Spitzer puede verlo. Los resultados serán publicados en el diario astrofísico y reflejan lo que sabemos sobre la formación de nuestro propio sistema planetario, añadió George Rieke. Las recientes observaciones sobre el estudio de nuestros cráteres de impacto en la Luna también revelan una temprana turbulencia en el Sistema Solar. Nuestra Luna tomó muchos golpes violentos cuando los planetas habían comenzado ya a tomar forma, dijo Rieke. Según la teoría más popular, los planetas rocosos comienzan su formación desde el exterior, alrededor de las estrellas jóvenes como minúsculas bolas en un campo de polvo grueso. Entonces, mediante uniones con otros granos de polvo, acumulan gradualmente una mayor cantidad de masa. http://www.cronica.com.mx/nota.php?idc=149166

18/Oct/04 Hallan un cúmulo globular oculto, un fósil de la galaxia (Astroseti) Precisamente cuando los astrónomos pensaban que ya habían desenterrado el último de los "fósiles" de nuestra galaxia, han descubierto uno nuevo en el equivalente galáctico de nuestro patio trasero. Llamados cúmulos globulares, estos antiguos conjuntos de estrellas datan de la época del nacimiento de la Vía Láctea, hace unos 13 mil millones de años. Están diseminados alrededor del centro de la galaxia como las semillas de un melón. Los astrónomos utilizan a los cúmulos como herramientas para el estudio de la edad y formación de nuestra galaxia. Nuevas imágenes infrarrojas obtenidas por el Telescopio Espacial Spitzer de la NASA y el Observatorio Infrarrojo de la Universidad de Wyoming revelan un cúmulo globular nunca antes visto dentro de los polvorientos confines de la Vía Láctea. Un informe acerca de sus hallazgos será publicado en un próximo número de la revista Astronomical Journal. "Es como encontrarse con un primo lejano a quien considerábamos perdido", dijo el Dr. Chip Kobulnicky, un profesor de física y astronomía de la Universidad de Wyoming, Laramie, y autor principal del informe. "Pensábamos que ya habían sido localizados todos los cúmulos globulares de la galaxia". "No podía creer lo que estaba viendo", dijo Andrew Monson, un estudiante graduado de la Universidad de Wyoming, quien fue el primero en detectar al cúmulo. "Ciertamente, no esperaba encontrar algo así". Este recién llegado es uno de los aproximadamente 150 cúmulos conocidos que orbitan alrededor de la Vía Láctea. Estos apretados nódulos de estrellas se encuentran entre los objetos más antiguos de la galaxia, habiéndose formado hace entre 10 a 13 mil millones de años. Contienen varios centenares de miles de estrellas, la mayoría de las cuales son más antiguas y menos masivas que el Sol. Monson divisó por primera vez al cúmulo mientras examinaba datos provenientes del Legado Galáctico de la Inspección Infrarroja Extraordinaria del Plano Medio, del Telescopio Espacial Spitzer, una investigación en busca de objetos escondidos dentro del polvoriento plano medio de nuestra galaxia. Posteriormente, buscó una correspondencia entre los archivos de datos y halló solamente una imagen indocumentada de un cúmulo proveniente de una previa inspección infrarroja del cielo financiada por la NASA, llamada Inspección Total del Cielo en Dos Micrones. "El cúmulo estaba allí, entre los datos, pero nadie lo había encontrado", dijo Monson. "Este descubrimiento demuestra por qué el Spitzer es tan poderoso: puede ver objetos que están completamente escondidos a la luz visible", dijo el Dr. Michael Werner del Laboratorio de Propulsión a Chorro (JPL) de la NASA en Pasadena, California, científico de proyecto para Spitzer. "Esto es particularmente relevante para el estudio del plano de nuestra galaxia, donde el polvo bloquea la mayor parte de la luz visible". Observaciones subsiguientes realizadas con el Observatorio Infrarrojo de la Universidad de Wyoming ayudaron a fijar la distancia a la Tierra del nuevo cúmulo en unos 9.000 años luz (más cerca que la mayoría de los otros cúmulos) y establecer su masa en el equivalente de unos 300.000 Soles. El tamaño aparente del cúmulo, tal como se lo ve desde nuestro planeta, es comparable al de un grano de arroz sostenido en la mano con el brazo extendido. Está localizado en la constelación del Águila. El equipo investigador consiste en astrónomos de la Universidad de Wisconsin, Madison; de la Universidad de Boston, en Boston, Massachusetts; de la Universidad de Maryland, College Park, Maryland; de la Universidad de Minnesota, Twin Cities; del Instituto de Ciencia Espacial, Boulder, Colorado; y del Centro de Ciencia de Spitzer, en Pasadena, California. El Legado Galáctico de la Inspección Infrarroja Extraordinaria del Plano Medio es manejado por la Universidad de Wisconsin y dirigido por el Dr. Ed Churchwell. JPL maneja la misión del Telescopio Espacial Spitzer para el Directorio de Misión Científica de la NASA, Washington, DC. Las operaciones científicas se llevan a cabo en el Centro de Ciencia Spitzer en el Instituto de Tecnología de California en Pasadena. JPL es una división de Caltech. El conjunto cámara infrarroja de Spitzer, que capturó la imagen del nuevo cúmulo, fue construido por el Centro Goddard de Vuelo Espacial de NASA en Greenbelt, Maryland. El desarrollo de la cámara fue dirigido por el Dr. Giovanni Fazio del Centro Harvard-Smithsoniano para Astrofísica, en Cambridge, Massachusetts. http://axxon.com.ar/not/143/c-1430151.htm

Survivor Found From Tycho's Supernova Summary - (Oct 28, 2004) Using the Hubble Space Telescope, astronomers have located what they think is the burned out star at the heart of Tycho's Supernova Remnant, which exploded in 1572. This discovery provides the first direct evidence that these kind of supernovae, called Type 1a, occur when a white dwarf consumes material from a binary companion until it reaches a certain point and explodes. They discovered the star, which is similar to our own Sun, because it's moving away from the explosion three times faster than other objects in the region - it was sling shotted away when its dancing partner vapourized. Full Story - An international team of astronomers is announcing today that they have identified the probable surviving companion star to a titanic supernova explosion witnessed in the year 1572 by the great Danish astronomer Tycho Brahe and other astronomers of that era. This discovery provides the first direct evidence supporting the long-held belief that Type Ia supernovae come from binary star systems containing a normal star and a burned-out white dwarf star. The normal star spills material onto the dwarf, which eventually triggers an explosion. The results of this research, led by Pilar Ruiz-Lapuente of the University of Barcelona, Spain, are being published in the Oct. 28 British science journal Nature. "There was no previous evidence pointing to any specific kind of companion star out of the many that had been proposed. Here we have identified a clear path: the feeding star is similar to our Sun, slightly more aged," Ruiz-Lapuente says. "The high speed of the star called our attention to it," she added. Type Ia supernovae are used to measure the history of the expansion rate of the universe and so are fundamental to helping astronomers understand the behavior of dark energy, an unknown force that is accelerating the expansion of the universe. Finding evidence to confirm the theory as to how Type Ia supernovae explode is critical to assuring astronomers that the objects can be better understood as reliable calibrators of the expansion of space. The identification of the surviving member of the stellar duo reads like a crime scene investigation tale. Even though today's astronomers arrived at the scene of the disaster 432 years later, using astronomical forensics they have nabbed one of the perpetrators rushing away from the location of the explosion (which is now enveloped in a vast bubble of hot gas called Tycho's Supernova Remnant). For the past seven years the runaway star and its surroundings were studied with a variety of telescopes. The Hubble Space Telescope played a key role by precisely measuring the star's motion against the sky background. The star is breaking the speed limit for that particular region of the Milky Way Galaxy by moving three times faster than the surrounding stars. Like a stone thrown by a sling, the star went hurtling off into space, retaining the velocity of its orbital motion when the system was disrupted by the white dwarf's explosion. This alone is only circumstantial evidence that the star is the perpetrator because there are alternative explanations to its suspicious behavior. It could be falling in at a high velocity from the galactic halo that surrounds the Milky Way's disk. But spectra obtained with the 4.2-meter William Herschel Telescope in La Palma and the 10-meter W.M. Keck telescopes in Hawaii show that the suspect has the high heavy-element content typical of stars that dwell in the Milky Way's disk, not the halo. The star found by the Ruiz-Lapuente team is an aging version of our Sun. The star has begun to expand in diameter as it progresses toward a red-giant phase (the end stage of a Sun-like star's lifetime). The star turns out to fit the profile of the perpetrator in one of the proposed supernova conjectures. In Type Ia supernova binary systems, the more massive star in the pair will age faster and eventually becomes a white dwarf star. When the slower-evolving companion star subsequently ages to the point where it begins to balloon in size, it spills hydrogen onto the dwarf. The hydrogen accumulates until the white dwarf reaches a critical and precise mass threshold, called the Chandrasekhar limit, where it explodes as a titanic nuclear bomb. The energy output of this explosion is so well known that it can be used as a standard candle for measuring vast astronomical distances. (An astronomical "standard candle" is any type of luminous object whose intrinsic power is so accurately determined that it can be used to make distance measurements based on the rate the light dims over astronomical distances). "Among the various systems containing white dwarfs that receive material from a solar-mass companion, some are believed to be viable progenitors of Type Ia supernovae, on theoretical grounds. A system called U Scorpii has a white dwarf and a star similar to the one found here. These results would confirm that such binaries will end up in an explosion like the one observed by Tycho Brahe, but that would occur several hundreds of thousands of years from now," says Ruiz-Lapuente. An alternative theory of Type Ia supernovae is that two white dwarfs orbit each other, gradually losing energy through the emission of gravitational radiation (gravity waves). As they lose energy, they spiral in toward each other and eventually merge, resulting in a white dwarf whose mass reaches the Chandrasekhar limit, and explodes. "Tycho's supernova does not appear to have been produced by this mechanism, since a probable surviving companion has been found," says Alex Filippenko of the University of California at Berkeley, a co-author on this research. He says that, nevertheless, it is still possible there are two different evolutionary paths to Type Ia supernovae. On November 11, 1572, Tycho Brahe noticed a star in the constellation Cassiopeia that was as bright as the planet Jupiter (which was in the night sky in Pisces). No such star had ever been observed at this location before. It soon equaled Venus in brightness (which was at -4.5 magnitude in the predawn sky). For about two weeks the star could be seen in daylight. At the end of November it began to fade and change color, from bright white to yellow and orange to faint reddish light, finally fading away from visibility in March 1574, having been visible to the naked eye for about 16 months. Tycho's meticulous record of the brightening and dimming of the supernova now allows astronomers to identify its "light signature" as that of a Type Ia supernova. Tycho Brahe's supernova was very important in that it helped 16th-century astronomers abandon the idea of the immutability of the heavens. At the present time, Type Ia supernovae remain key players in the newest cosmological discoveries. To learn more about them and their explosion mechanism, and to make them even more useful as cosmological probes, a current Hubble Space Telescope project led by Filippenko is studying a sample of supernovae in other galaxies at the very time they explode. Original Source: Hubble News Release http://www.universetoday.com/am/publish/tycho_supernova_survivor.html?28102004

What's Up This Week? Nov 1 - 7, 2004 Summary - (Nov 1, 2004) Hello fellow stargazers and welcome to this week's edition of what's new and fun to do under the skies. For all of you who took the time to view last week's total lunar eclipse? Congratulations! This week's planetary actions will blow you away. On the 3rd, the real "Lord of the Rings" - Saturn - will accompany the Moon across the night. The solar system excitement continues as before local dawn on November 4th and 5th will be a superb visual pairing of Venus and Jupiter at less than one degree apart. The Southern Taurid meteor stream will be active and it has produced fantastic fireballs seen around the world! For those of you craving a bit of deep sky work? The time is right to do a little "Wild Duck" hunting. Here's what's up! Full Story - Monday, November 1 - As the new month begins, we've already began to feel the impact of the shorter daylight hours and I am sure many of you have noticed the migration of the birds. What better time to explore the infamous "Wild Duck" cluster than in the short span of time we have tonight before the Moon rises? Discovered in 1681 by German astronomer, Gottfried Kirch, at the Berlin Observatory, M11 was later cataloged by Charles Messier in 1764 and first dubbed the "Wild Ducks" by Admiral Smyth. To our modern telescopes and binoculars, there is little doubt as to how this rich galactic cluster earned its name - for it has a distinctive wedge-shaped pattern that closely resembles a flight of ducks. This fantastic open cluster of several thousand stars (about 500 of them are magnitude 14 or brighter) is approximately 250 million years old! M11 is easily located by identifying our last week's study object - Altair. By counting two stars "down" the "body" of Aquila and stopping on Lambda you will find your starhop "guide". Near Lambda you will see three stars, the centermost is Eta Scuti. Now just aim! Even small binoculars will have no problem finding M11, but a telescope is required to start resolving individual stars. The larger the telescope's aperture the more stars will be revealed. Tuesday, November 2 - Tonight will be a great opportunity before the Moon rises to try your hand at finding Uranus and Neptune. Uranus will be fairly easy to spot in small binoculars just due west Sigma Aquarii. At a respectable magnitude 5.8, it will appear to this low power view as a blue/green "star", but telescopes will reveal its 3.5" disc with no problem. At magnitude 7.9, Neptune is harder to find, but not impossible in moderately dark skies. The key to finding Neptune is to locate bright Alpha and Beta in Capricornus' northwest corner. From there, drop due south to find a close grouping of three stars. Now go due west until you spot moderately bright Theta about central in the constellation. Theta will be your guide and you will find Neptune west/northwest of it by using a more detailed locator chart. Neptune will appear as a small (2.3" diameter) blue-grey disk to higher power, but that's pretty remarkable considering it's over four and half billion kilometers away from the Sun! Don't think that's challenge enough? Then large telescope owners and webcam "hot shots" are encouraged to try for Neptune's most visible moon, Triton, at magnitude 13. Best of luck! Wednesday, November 3 - For those of you who have awaited the chance to find Saturn easily? Then tonight is your night. Rising by local midnight the waning Moon will be your guide to finding Saturn - for the "Ring King" will appear about 6 degrees south. (If you can't stay up that late? Don't worry! The pair will still be there before dawn.) Saturn is absolutely magnificent in even the smallest of telescopes. Its amazing ring system and bright moon Titan are easily perceived at modest magnification and even larger binoculars will reveal its planetary nature. Larger telescopes will appreciate Saturnian features such as the Cassini division and shadow of the planet against the ring system. Moon viewer's will also appreciate tonight's highlighted view of the Apennine Mountain range. Stretching a massive distance of 750 km (450 miles) the Apennine Mountain range makes up the south east wall of Mare Ibrium. Truly a delight! On November 3, 1957 the Russian Space Program launched its first "live" astronaut into space - Laika. Carried on board Sputnik 2, our canine hero was the first living creature to reach orbit. The quickly developed Sputnik 2 was designed with sensors to transmit ambient pressure, breathing patterns and heartbeat of its passenger along with a television camera monitor. The craft also monitored ultraviolet and x-ray radiation as well to further study the impact of space flight upon human occupants. Unfortunately, the technology of the time offered no way to return Laika to Earth, so she perished in space. On April 14, 1958, Laika and Sputnik 2 returned to Earth in a fiery re-entry ending after 2,570 orbits. Thursday, November 4 - Prepare yourself for this week's exciting astronomical event! Before local sunrise this morning, bright Venus and returning Jupiter will make a dazzling appearance in the eastern sky as they appear around one half a degree apart! This spectacular display will delight viewers of all ages and skill levels. Very visible to the naked eye, this bright pairing will offer outstanding photographic opportunities and well as a memorable observing experience through either telescopes or binoculars. This morning will be the peak of the Southern Taurid meteor shower. Already making headlines around the world for producing fireballs, the Taurids will be best visible in the earlier evening hours before moonrise. The radiant for this shower is, of course, the constellation of Taurus and red giant Aldeberan, but did you know the Taurids are divided into two streams? It is surmised that the original parent comet shattered as it passed our Sun around 20,000 to 30,000 years ago. The larger "chunk" continued orbiting and is known as periodic comet Encke. The remaining debris field turned into smaller asteroids, meteors and larger fragments that often pass through our atmosphere creating astounding "fireballs" known as bolides. Although the fall rate for this particular shower is rather low at 7 per hour, these slow traveling meteors (27km or 17 miles per second) are usually very bright and appear to almost "trundle" across the sky. With the chances high all week of seeing a bolide, this makes a bit of quiet contemplation under the stars a worthy evening. While you are out meteor watching, take the opportunity to check out the Moon. Tonight's highlighted features will be craters Pltomaeus, Alphonsus and Arzachel. Image credit: NASA Friday, November 5 - Did you miss your opportunity to see Venus and Jupiter yesterday? Then don't despair for the pair will still be very visible in the pre-dawn skies this morning as well. They've just changed positions slightly! Two additional challenges for this morning is the appearance of Mars low on the horizon and the return of Comet LINEAR C/2003 K4. Viewers with an open horizon to the east/south east are strongly encouraged to take out even the smallest of binoculars or telescopes and attempt to find Comet K4 in the basic center of the constellation of Corvus. The four primary stars of Corvus are easy to recognize and finding the comet should be a cinch. The two southernmost stars are Beta and Epsilon - almost directly between them and slightly to the north is Theta. It is around this star your will find the comet! Starting November 1, K4 will be north of Theta and will be slightly southwest of it on this date. At predicted magnitude 5, this bright comet is on the verge of naked-eye visibility and will be a snap to find with binoculars. For Moonwatchers tonight, take the opportunity to revisit the "Straight Wall". While we learned about Rupes Recta during the waxing phase two weeks ago, the waning phase will create the finest appearance of the "Straight Wall" this month. Saturday and Sunday, November 6 and 7 - Thanks to the later rise of the Moon this weekend, right now would be a great time to think "all about Andromeda". The first of our objects for tonight can be a naked-eye observation from a dark sky site, an easy catch with binoculars even from urban locations and absolutely outstanding in telescopes. Of whom do I speak so highly? Why, of the Great Andromeda Galaxy of course! For those of you just beginning in astronomy, you owe it to yourself to find a dark sky location and try locating a galaxy whose light left almost 3 million years ago with just your eyes! Although I have provided you with a map, it's not always as easy to use one as it may seem. If you are having difficulties, try this simple trick. About an hour or so after the Sun sets and the skies are completely dark, go out and face east. About halfway between the horizon and the zenith, look for a wide pattern of four stars that resemble a large diamond. This is the Great Square of Pegasus! To the left of you, look for the flattened M of the constellation of Cassiopeia. Now, returning to the Great Square, focus on the left hand star and point at it. Moving left, count this as one bright star. Going left, two - a much dimmer one, and more left, three, a bright one - and stop. Above this star (and toward Cassiopeia) you will see another star, and above that? A hazy, fuzzy patch of glow that is the Andromeda Galaxy! As far back as 905 A.D., this galaxy has been known as "The Little Cloud" and appeared on ancient star charts long before the telescope was even dreamed of. It also appeared on Dutch starmaps as far back as 1500, but wasn't cataloged by Messier until August 3, 1764. One of the first telescopic descriptions actually dates back to 1612! Even the great Edmond Halley in 1716 credited its discovery incorrectly to French astronomer Bullialdus in 1661, even though it had been reported 150 years earlier. Image credit: NASA As a part of our own "Local Group" of eleven galaxies, the Andromeda galaxy is our nearest large neighbor. Both it and our own Milky Way are approaching each other at about 100 km per second. But not to worry - the M31 is still almost 2.9 million light years away! Now, focus binoculars on the area and be prepared to journey across space and time... Small telescopes and binoculars at low power will have no trouble seeing the M31's bright nucleus and 4 degrees of extension. Larger binoculars and mid-range telescopes will find that the Andromeda contains a triple treat, as the M32 and M110 galaxies also accompany it. For those of you with large telescopes who scoff at such a simple target as the Andromeda? Then I highly encourage you to "power up" and study the NGC206 on the M31's southern flank. This region of nebulosity and starbirth is a challenge object worthy of your optics and you'll be studying a DSO in another galaxy! While you're in the neighborhood? Take the time to study the map and visit with Gamma Andromeda. Almach is a wonderful double star, and its yellowish primary and blue-green secondary are easily split by modest telescopes. Again, for those of you with larger telescopes and precision optics there's another challenge here. Almach's secondary star is also a double! Until next week fellow stargazers? Keep looking up! I wish you clear skies and light speed... ~Tammy Plotner http://www.universetoday.com/am/publish/whats_up_nov1_2004.html?1112004

First Gamma Ray Image Summary - (Nov 4, 2004) European astronomers have produced the first image of an object using high energy gamma rays - the most penetrating form of radiation known. The image is of a supernova remnant called RX J1713.7-3946, which exploded 1,000 years ago. Over time, a ring of material has expanded to twice the diameter of the Moon in the sky. If you had gamma ray eyes, you would be able to see a large ring in the sky every night. This also helps solve a 100 year mystery about the origin of cosmic rays; the remnant seems to be acting as a particle accelerator. Full Story - A team of UK astronomers working with international partners has produced the first ever image of an astronomical object using high energy gamma rays, helping to solve a 100 year old mystery - the origin of cosmic rays. Their research, published in the Journal Nature on November 4th, was carried out using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa. The astronomers studied the remnant of a supernova that exploded some 1,000 years ago, leaving behind an expanding shell of debris which, seen from the Earth, is twice the diameter of the Moon. The resulting image helps to solve a mystery that has been puzzling scientists for almost 100 years - the origin of cosmic rays. Cosmic rays are extremely energetic particles that continually bombard the Earth, thousands of them passing through our bodies every day. The production of gamma rays in this supernova shock wave tells us that it is acting like a giant particle accelerator in space, and thus a likely source of the cosmic rays in our galaxy. Dr Paula Chadwick of the University of Durham said "This picture really is a big step forward for gamma-ray astronomy and the supernova remnant is a fascinating object. If you had gamma-ray eyes and were in the Southern Hemisphere, you could see a large, brightly glowing ring in the sky every night." Professor Ian Halliday, CEO of PPARC which funds UK participation in HESS said "These results provide the first unequivocal proof that supernovae are capable of producing large quantities of galactic cosmic rays - something we have long suspected, but never been able to confirm." Gamma rays are the most penetrating form of radiation we know, around a billion times more energetic than the X-rays produced by a hospital X-ray machine. This makes it very difficult to use them to create an image - they just pass straight through any surface which we might use to reflect them, for instance. However, luckily for life on Earth, gamma rays from objects in outer space are stopped by the atmosphere; when this happens, a faint flash of blue light is produced, lasting for a few billionths of a second. The astronomers used images of these flashes of light, called Cherenkov radiation, to make a gamma ray 'image' for the first time. Original Source: PPARC News Release http://www.universetoday.com/am/publish/first_gamma_ray_image.html?4112004

November 3, 2004 | On November 11, 1572, Tycho Brahe noted the appearance of a bright new star in the constellation Cassiopeia. This startling sight challenged the popular Aristotelian view of an unchanging heavens and perhaps even contributed to the opening scene of Shakespeare's Hamlet. Today we recognize this "new star" as the most recent of only two Type Ia supernovae recorded within our galaxy. A Type Ia supernova is thought to occur when a white dwarf in a binary-star system steals matter from its companion, probably a normal Sun-like star or a red giant. When the white dwarf exceeds 1.4 solar masses, a runaway thermonuclear reaction in its core blows it apart. But astronomers are uncertain about how the white dwarf manages to accrete gas from its companion without igniting as a classical nova, in which material undergoes nuclear fusion on its surface. Because of this puzzle, a few scientists have argued that some or all Type Ia supernovae result from two white dwarfs merging. An international team led by Pilar Ruiz-Lapuente (University of Barcelona, Spain) reports in the October 28th Nature that it has found the companion star that triggered Tycho's supernova. The team measured the relative velocities of stars in the glowing supernova remnant, located about 10,000 light-years away, in hopes of finding the companion star that pushed the white dwarf over the edge. The surviving donor star would have fled the scene like a stone flung from a sling, retaining its orbital velocity at the time of the explosion. Using both ground-based telescopes and the Hubble Space Telescope, they found a Sun-like star (named Tycho G) at the right place that is moving three times faster than the surrounding stars. The arrowed star in the Hubble Space Telescope image (right) is Tycho G, a fast-moving star that might be the companion to the white dwarf that was seen to explode in 1572. Tycho G is similar to the Sun but several billion years older. It is noticeably offset (by 2.6 arcseconds) from the center of the supernova remnant. Its motion is much faster than that of any other star in its neighborhood. Courtesy NASA / ESA / CXC / Pilar Ruiz-Lapuente. "There was no previous evidence pointing to any specific kind of companion star out of the many that had been proposed," says Ruiz-Lapuente. "Here we have identified a clear path: the feeding star is similar to our Sun, but slightly more aged. The high speed of the star called our attention to it." "I would not bet my house on it, but this appears to be the best candidate for the progenitor's companion," says independent commentator Mario Livio (Space Telescope Science Institute). "It certainly is moving fast, but that is about all that it has going for it. It is not moving phenomenally fast; nor does it appear to have an unusual composition." Future observations may reveal evidence, such as an iron-rich supernova ejecta signature in Tycho G's spectrum, to verify that the star was the donor. But Livio cautions, "There are not many options to confirm this completely unambiguously. We may be left with a tantalizing possibility that it is the companion, but without knowing for certain." If Tycho G is indeed the survivor of Tycho's supernova, it would provide the first direct evidence that astronomers are on the right track to understanding Type Ia supernovae. In particular, it would exclude the possibility that all Type Ia's are merging white dwarfs. It would also prove that not all progenitor companions are red giants. A confirmation would also have ramifications for cosmology. Type Ia supernovae have extremely bright and predictable luminosities, making them ideal "standard candles" for measuring the expansion of the universe. Observations of these explosions in distant galaxies have led astronomers to the startling conclusion that cosmic expansion is accelerating. Livio points out that astronomers have calibrated the luminosities of Type Ia supernovae accurately, and observations from WMAP and other microwave background experiments independently support an accelerating universe. "Still, it has been somewhat unacceptable that we did not know what Type Ia supernova progenitors are," he says. http://skyandtelescope.com/news/article_1383_1.asp

Asteroids Tell Tale of Jupiter Migration By Robert Naeye Scientists assembled this Jupiter mosaic from a series of Cassini images taken during the December 2000 flyby. New research suggests that Jupiter formed farther from the Sun and migrated in to its present orbit. Courtesy NASA / JPL / Space Science Institute. November 1, 2004 | In 1984 astrophysicists Julio A. Fernández and Wing-Huen Ip wrote a seminal paper arguing that the outer planets of the solar system migrated from where they formed to where they are today. To understand how this could occur, consider gravity assists, such as the Cassini spacecraft's December 30, 2000, flyby of Jupiter. Like a table-tennis ball hitting a rotating ceiling fan and speeding up, Cassini was flung forward an extra 2 kilometers per second by Jupiter's gravitational field. This speeded up the spacecraft's Saturn arrival by several months. But tiny Cassini pulled on mighty Jupiter too, decreasing the planet's orbital momentum by a paltry 1 meter per 6 trillion years. The planet drifted inward by an amount so tiny it would be impossible to measure with a microscope. That might not sound like much, but in the early days of the solar system, the outer planets experienced trillions of close encounters with small, icy planetesimals. While any one encounter had a negligible effect on a planet, they added up. Fernández and Ip showed that Jupiter must have launched more bodies outward than inward. Some of the outward-bound objects ended up in the Oort Cloud; others were thrown into interstellar space. In response, Jupiter must have migrated inward by perhaps 0.2 astronomical unit (20 percent the average Earth-Sun distance) over the course of about 100,000 years. Now Fred A. Franklin and a team at the Harvard-Smithsonian Center for Astrophysics have found present-day evidence for a migrating Jupiter long ago. In computer simulations, Franklin and his colleagues discovered that an inwardly migrating Jupiter reproduces the observed orbital characteristics of the 700 known Hilda asteroids. These bodies, which belong to a distinct family with similar orbits and compositions, are trapped in a 3:2 mean-motion resonance with Jupiter — meaning that over the long run they go around the Sun exactly three times every time Jupiter goes around twice. In addition, almost all Hildas have modest orbital eccentricities between 0.1 and 0.25. White dots represent the positions of roughly 700 known Hilda-family asteroids at a particular moment in time. The yellow ellipses show orbits of three of them. The eccentricities and other characteristics of Hilda asteroids offer evidence that Jupiter drifted sunward during the early days of the solar system. S&T diagram by Gregg Dinderman. Source: Petr Scheirich. The team's computer simulations show that an inwardly migrating Jupiter would have shepherded large numbers of asteroids into 3:2 resonant orbits. These objects would have remained stuck in the relationship even as Jupiter spiraled inward. The distribution of Hilda orbits requires a long Jovian migration time scale of at least 100,000 years. Moreover, Jupiter must have migrated inward by at least 0.35 a.u., and more likely 0.45 a.u., for the process to work. Jupiter currently resides at an average distance of 5.2 a.u. (484 million miles, or 779 million kilometers) from the Sun. This relatively large migration caused low-eccentricity would-be Hildas to be ejected, which explains the virtual absence of any family members with eccentricities less than 0.1. Such a migration also successfully replicates the observed distribution of the Hildas that lie inside the 3:2 resonance itself. The group's work appears in the September 2004 Astronomical Journal. "Up to now, studies of Jovian migration have relied on computer simulations of what might have happened in the very early days of the solar system," says Franklin. "The current work is different in an important regard: it is observationally based. We are seeking an explanation of a current solar-system phenomenon that has no other known explanation." Comments dynamicist Renu Malhotra (University of Arizona), "The paper is significant in that it adds to the support for Jupiter's inward migration and provides one of the few quantitative constraints on the magnitude of that migration." http://skyandtelescope.com/news/article_1382_1.asp

Where Cosmic Rays Come From HESS gamma-ray image of supernova remnant Credit: HESS European astronomers have produced the first image of an object using high energy gamma rays - the most penetrating form of radiation known. The image is of a supernova remnant called RX J1713.7-3946, which exploded 1,000 years ago. Over time, a ring of material has expanded to twice the diameter of the Moon in the sky. If you had gamma ray eyes, you would be able to see a large ring in the sky every night. This also helps solve a 100 year mystery about the origin of cosmic rays; the remnant seems to be acting as a particle accelerator. During Earth's earliest history, its surface also was bombarded by high-energy particles associated with solar activity (from a solar wind that was enhanced during early history and from solar flares) and galactic cosmic rays, and possibly from nearby supernovae and events associated with gamma-ray bursts. This bombardment must have had deleterious effects on life at the Earth's surface, and may have severely affected the formation and earliest evolution of life. The latest result, published in the Journal Nature on November 4th, was carried out using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa. Dr Paula Chadwick of the University of Durham said "This picture really is a big step forward for gamma-ray astronomy and the supernova remnant is a fascinating object. If you had gamma-ray eyes and were in the Southern Hemisphere, you could see a large, brightly glowing ring in the sky every night." Dr. John Horack, who led the assembly, testing and calibration program for the gamma ray burst experiment on NASA's Compton Gamma-Ray Observatory Credit: D. Rezabek Professor Ian Halliday, CEO of the UK-based Particle Physics and Astronomy Research Council said "These results provide the first unequivocal proof that supernovae are capable of producing large quantities of galactic cosmic rays - something we have long suspected, but never been able to confirm." To put the finding in perspective, Astrobiology Magazine had the opportunity to talk with John Horack, who led the assembly, testing and calibration program for the gamma ray burst experiment on NASA's Compton Gamma-Ray Observatory. -------------------------------------------------------------------------------- Astrobiology Magazine (AM): Have people been proposing a gamma-ray telescope for a long time, or is this possible now with newer technologies? John Horack (JH): There have been gamma-ray telescopes in the past, for example the COMPTEL experiment aboard NASA's Compton Gamma-Ray Observatory imaged the cosmos in gamma rays for nearly 10 years from low earth orbit. The breakthrough here, as I understand it, is that we are now making gamma ray images from the ground. AM: Presumably, seeing in a small wavelength window highlights the higher energy processes in the sky. Does it make sense to look at gamma ray bursts with a gamma ray telescope? JH: Gamma ray bursts are very different from supernova remnants, of course, but yes, it makes sense to try -- and scientists have been trying since their discovery in 1967. The problem with gamma ray bursts is that you do not know where the next one is coming from, and therefore trying to guess by pointing your telescope is kind of a shot in the dark. Early gamma-ray burst experiements used very wide fields fo view, and found the direction to bursts by working out the direction by studying the time difference in detection by widely-separated experiments in space. Later, experiements like BATSE on the Compton GRO used detectors that could see the entire sky at once, thereby capturing any gamma-ray burst of sufficient strength and determining the direction by the relative brightness in each of the eight detectors pointed in different directions. The Dutch-Italian BeppoSAX actually was able to catch gamma-ray bursts in real time by quickly slewing the telescope on the spacecraft after a detection. Today, experiments like the High Energy Transient Experiment (HETE) and SWIFT offer the best chances we've ever had to catch a gamma ray burst "in the act" either by detecting the gamma-ray or x-ray emission as the burst is occurring, or shortly after it has begun. HESS Gamma Ray Telescope. Cherenkov light develops within an air shower. Because the particle moves faster than the speed of light in air, there is a sonic boom or shock wave, which sends out a flash of blue light in the direction of the primary gamma quantum and lasts a few billionths of a second. This happens about ten kilometers (6.3 miles) above the earth's surface. Credit: Hess Collection AM: Because atmospheres shield gamma rays, could such gamma telescopes be turned to closer objects like Venus or Titan to pick off novel features of their atmospheres as opaque in this wavelength? JH: The Earth's atmosphere does prevent gamma-ray radiation from reaching the ground, and gamma-rays are usually associated with far more energetic objects such as black-holes, neutron stars, supernovae, and quasars. Turning a space-based gamma-ray telescope at a planet is not terribly useful, since these planets are "dark" in gamma-rays, and their angular sizes as seen from the Earth are incredibly small compared to the resolution of a gamma-ray telescope. In gamma-rays, the Sun isn't even the brightest object in the sky. The Crab Nebula, Cygnus X-1, and a host of other sources typically are brighter in gamma-rays. The universe is just far too plentiful in exotic, energetic, and explosive phenomena to spend time trying to detect gamma-rays from Venus. One thing that was learned from BATSE, however, is that thunderstorms on Earth do create large but short-lived flashes of intense, upward-moving gamma radiation observable from low-earth orbit. This was a total surprise, and one of those kinds of discoveries that happen in science that one would never have predicted prior to the launch of BATSE in 1991. AM: One question that is curious about HESS and its relation to gamma ray detectors of the past, is the basis for having a space telescope. How does HESS see such objects when the atmosphere is opaque--is it looking for byproducts in the upper atmosphere, like Cerenkov radiation, thus making it more of a Cerenkov eye, not a true gamma eye? JH: HESS does not detect the gamma-rays directly, since they do not reach the ground. So yes, it is detecting the evidence of a gamma-ray, not the gamma-ray itself. Crab Nebula in X-rays showing its main central jet. Credit: NASA This evidence is called Cerenkov radiation, produced when an object such as a high-energy particle moves faster than the speed of light in the medium it is travelling through. Please note, this speed is NEVER faster than the speed of light in a vacuum. As an example, the speed of light in water is slower than the speed of light in a vacuum. Nothing can travel faster than the speed of light in a vacuum. But if you move an electron through water at a speed less than the vacuum speed, but more than water velocity, it will emit radiation that can be detected, called Cerenkov radiation. This is what HESS is detecting, from particles created through interactions between the incoming gamma-rays and the upper atmosphere. AM: The origin of cosmic rays are being attributed to supernova, because of a glowing ring. Aren't there theories that cosmic rays are just accelerated in the plasma of a supernova, not originating there? JH: The origin of cosmic rays is a long-standing question, and the prediction of an association between cosmic rays and supernovae dates back to the late 1930's. So this result helps put that question to bed, and may allow scientists to get on with understanding the detailed physics of how the production takes place in this environment. AM: Any ideas for where to point this next, like at our Sun or even burst afterglows? JH: I'd love to see some Northern hemisphere objects, such as the Crab Nebula, Cygnus X-1, or the possibility of detection of things like X-ray transients from the Galactic Center. In fact, this is one of the most interesting things about the high-energy sky: it changes very frequently, and the brightest object in the sky today, might not be the brighest object in the sky tomorrow. Things can change on timescales of minutes, days, or weeks. -------------------------------------------------------------------------------- The HESS telescopes are ten times more sensitive than earlier Cherenkov telescopes. Each HESS collector has a diameter of twelve meters (~40 feet) and 380 individual round mirrors that make up a light-collecting surface area of 108 square meters (~1000 sq. ft.). The camera enables exposure times of a mere one hundred millionth of a second. The HESS acronym alludes to the Austrian physicist Viktor Franz Hess (1883-1964) who discovered cosmic rays during ten balloon flights between 1911 and 1913. In 1936, he was awarded the Nobel Prize for Physics. Related Web Pages Long, Strange Trips Astrobiology Roadmap Long, Strange Trips Black Hole Broadcasting Hypernova Blast The Catalog and Atlas of Cataclysmic Variables Automated Telescope Grids, Instant Messages The Mystery of Standard Candles Inevitability Beyond Billions Note: Stellar Evolution http://www.astrobio.net/news/article1288.html

PRESS RELEASE Date Released: Wednesday, November 10, 2004 Source: Jet Propulsion Laboratory NASA Spitzer Sees Ice and Warm Glows in Dark and Dusty Places Two new results from NASA's Spitzer Space Telescope released today are helping astronomers better understand how stars form out of thick clouds of gas and dust, and how the molecules in those clouds ultimately become planets. Two discoveries -- the detection of an oddly dim object inside what was thought to be an empty cloud, and the discovery of icy planetary building blocks in a system believed to resemble our own solar system in its infancy -- were presented today at the first Spitzer science conference in Pasadena, Calif. Since Spitzer science observations began less than one year ago, the infrared capabilities of the space observatory have unveiled hundreds of space objects too dim, cool or distant to be seen with other telescopes. In one discovery, astronomers have detected a faint, star-like object in the least expected of places -- a "starless core." Named for their apparent lack of stars, starless cores are dense knots of gas and dust that should eventually form individual newborn stars. Using Spitzer's infrared eyes, a team of astronomers led by Dr. Neal Evans of the University of Texas at Austin probed dozens of these dusty cores to gain insight into conditions that are needed for stars to form. Starless cores are fascinating to study because they tell us what conditions exist in the instants before a star forms. Understanding this environment is key to improving our theories of star formation, said Evans. But when they looked into one core, called L1014, they found a surprise -- a warm glow coming from a star-like object. The object defies all models of star formation; it is fainter than would be expected for a young star. Astronomers theorize that the mystery object is one of three possibilities: the youngest "failed star," or brown dwarf ever detected; a newborn star caught in a very early stage of development; or something else entirely. This object might represent a different way of forming stars or brown dwarfs. Objects like this are so dim that previous studies would have missed them. It might be like a stealth version of star formation, Evans said. The new object is located 600 light-years away in the constellation Cygnus. In another discovery, Spitzer's infrared eyes have peered into the place where planets are born -- the center of a dusty disc surrounding an infant star -- and spied the icy ingredients of planets and comets. This is the first definitive detection of ices in planet-forming discs. This disc resembles closely how we imagine our own solar system looked when it was only a few hundred thousand years old. It has the right size, and the central star is small and probably stable enough to support a water-rich planetary system for billions of years into the future, said Dr. Klaus Pontoppidan of Leiden Observatory in the Netherlands, who led the team that made this discovery. Previously, astronomers had seen ices, or ice-coated dust particles, in the large cocoons of gas and dust that envelop young stars. But they were not able to distinguish these ices from those in the inner planet-forming portion of a star's disc. Using Spitzer's ultra-sensitive infrared vision and a clever trick, Pontoppidan and his colleagues were able to overcome this challenge. Their trick was to view a young star and its dusty disc at "dawn." Discs can be viewed from a variety of angles, ranging from the side or edge-on, where the discs appear as dark bars, to face-on, where the discs become washed out by the light of the central star. They found that if they observed a disc at a 20-degree angle, at a position where the star peeks out like our Sun at dawn, they could see the ices. "We hit the sweet spot," said Pontoppidan. "Our models predicted that the search for ices in discs is a problem of finding an object with just the right viewing angle, and Spitzer confirmed that model. In this system, astronomers found ammonium ions as well as components of water and carbon dioxide ice. The Spitzer science conference, "The Spitzer Space Telescope: New Views of the Cosmos," is being held at the Sheraton Pasadena hotel. JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington, D.C. Science operations are conducted at the Spitzer Science Center, Pasadena, Calif. JPL is a division of Caltech. For more information about Spitzer visit www.spitzer.caltech.edu . http://www.spaceref.com/news/viewpr.html?pid=15479

11/10/04, 10:24 (Hora de México DF) • Descubren segundo agujero negro en la Vía Láctea Londres, Reino Unido, 10 de noviembre. Astrónomos franceses descubrieron un segundo agujero negro en el centro de nuestra galaxia, la Vía Láctea, que tiene mil 300 veces la masa de Sol del Sistema Solar al que pertenece la Tierra y es relativamente pequeño, informó la revista científica Nature en su página web. Astrónomos franceses descubrieron un segundo agujero negro en el centro de nuestra galaxia, la Vía Láctea, que tiene mil 300 veces la masa de Sol del Sistema Solar al que pertenece la Tierra y es relativamente pequeño, informó la revista científica Nature en su página web. El equipo dirigido por Jean-Pierre Maillard, del Instituto de Astrofísica en París, observó siete estrellas que giran alrededor del agujero denominado IRS 13E. Así pudo identificarse indirectamente el objeto invisible. Hace tres años, astrónomos estadunidenses descubrieron en el centro de la Vía Láctea un gigantesco agujero negro denominado Sagitario A, que posee 2.6 millones de veces la masa del Sol. A tres años luz de allí el equipo francés descubrió a un familiar de Sagitario A, que en términos galácticos es prácticamente vecino. Los científicos analizaron, entre otros, imágenes infrarrojas del observatorio Gemini de Hawai. Los franceses creen que hay otros diminutos agujeros negros cerca de la Tierra. Los agujeros negros son objetos celestes que tienen una fuerza de gravedad tan fuerte que ni la luz puede escapar a ellos. Los investigadores franceses informan acerca de su descubrimiento en la revista especializada Astronomy and Astrophysics (volumen 423). En Internet: www.nature.com http://www.todito.com/paginas/noticias/164421.html

How Did the First Stars Form? Summary - (Nov 18, 2004) Early star formation is a bit of a puzzle for astronomers, since all the stars that we can see formed out of molecular gas and dust, which are produced in stars. How did the first ones form without any gas and dust? One class of galaxies, called Blue Dwarf Galaxies may offer some clues. They contain interstellar clouds which are similar to the material that would have been present in the early Universe. And these galaxies can have active regions of furious star formation. New research from the European Southern Observatory has targeted one of these Blue Dwarfs to try and understand the process better. Full Story - Star formation is one of the most basic phenomena in the Universe. Inside stars, primordial material from the Big Bang is processed into heavier elements that we observe today. In the extended atmospheres of certain types of stars, these elements combine into more complex systems like molecules and dust grains, the building blocks for new planets, stars and galaxies and, ultimately, for life. Violent star-forming processes let otherwise dull galaxies shine in the darkness of deep space and make them visible to us over large distances. Star formation begins with the collapse of the densest parts of interstellar clouds, regions that are characterized by comparatively high concentration of molecular gas and dust like the Orion complex (ESO PR Photo 20/04) and the Galactic Centre region (ESO Press Release 26/03). Since this gas and dust are products of earlier star formation, there must have been an early epoch when they did not yet exist. But how did the first stars then form? Indeed, to describe and explain "primordial star formation" - without molecular gas and dust - is a major challenge in modern Astrophysics. A particular class of relatively small galaxies, known as "Blue Dwarf Galaxies", possibly provide nearby and contemporary examples of what may have occurred in the early Universe during the formation of the first stars. These galaxies are poor in dust and heavier elements. They contain interstellar clouds which, in some cases, appear to be quite similar to those primordial clouds from which the first stars were formed. And yet, despite the relative lack of the dust and molecular gas that form the basic ingredients for star formation as we know it from the Milky Way, those Blue Dwarf Galaxies sometimes harbour very active star-forming regions. Thus, by studying those areas, we may hope to better understand the star-forming processes in the early Universe. Very active star formation in NGC 5253 NGC 5253 is one of the nearest of the known Blue Dwarf Galaxies; it is located at a distance of about 11 million light-years in the direction of the southern constellation Centaurus. Some time ago a group of European astronomers [1] decided to take a closer look at this object and to study star-forming processes in the primordial-like environment of this galaxy. True, NGC 5253 does contains some dust and heavier elements, but significantly less than our own Milky Way galaxy. However, it is quite extreme as a site of intense star formation, a profuse "starburst galaxy" in astronomical terminology, and a prime object for detailed studies of large-scale star formation. ESO PR Photo 31a/04 provides an impressive view of NGC 5253. This composite image is based on a near-infrared exposure obtained with the multi-mode ISAAC instrument mounted on the 8.2-m VLT Antu telescope at the ESO Paranal Observatory (Chile), as well as two images in the optical waveband obtained from the Hubble Space Telescope data archive (located at ESO Garching). The VLT image (in the K-band at wavelength 2.16 ?m) is coded red, the HST images are blue (V-band at 0.55 ?m) and green (I-band at 0.79 ?m), respectively. The enormous light-gathering capability and the fine optical quality of the VLT made it possible to obtain the very detailed near-infrared image (cf. PR Photo 31b/04) during an exposure lasting only 5 min. The excellent atmospheric conditions of Paranal at the time of the observation (seeing 0.4 arcsec) allow the combination of space- and ground-based data into a colour photo of this interesting object. A major dust lane is visible at the western (right) side of the galaxy, but patches of dust are visible all over, together with a large number of colourful stars and stellar clusters. The different colour shades are indicative of the ages of the objects and the degree of obscuration by interstellar dust. The near-infrared VLT image penetrates the dust clouds much better than the optical HST images, and some deeply embedded objects that are not detected in the optical therefore appear as red in the combined image. Measuring the size and infrared brightness of each of these "hidden" objects, the astronomers were able to distinguish stars from stellar clusters; they count no less than 115 clusters. It was also possible to derive their ages - about 50 of them are very young in astronomical terms, less than 20 million years. The distribution of the masses of the cluster stars ressembles that observed in clusters in other starburst galaxies, but the large number of young clusters and stars is extraordinary in a galaxy as small as NGC 5253. When images are obtained of NGC 5253 at progressively longer wavelengths, cf. ESO PR Photo 31c/04 which was taken with the VLT in the L-band (wavelength 3.7 ?m), the galaxy looks quite different. It no longer displays the richness of sources seen in the K-band image and is now dominated by a single bright object. By means of a large number of observations in different wavelength regions, from the optical to the radio, the astronomers find that this single object emits as much energy in the infrared part of the spectrum as does the entire galaxy in the optical region. The amount of energy radiated at different wavelengths shows that it is a young (a few million years), very massive (more than one million solar masses) stellar cluster, embedded in a dense and heavy dust cloud (more than 100,000 solar masses of dust; the emission seen in PR Photo 31c/04 comes from this dust). A view towards the beginnings These results show that a galaxy as tiny as NGC 5253, almost 100 times smaller than our own Milky Way galaxy, can produce hundreds of compact stellar clusters. The youngest of these clusters are still deeply embedded in their natal clouds, but when observed with infrared-sensitive instruments like ISAAC at the VLT, they stand out as very bright objects indeed. The most massive of these clusters holds about one million solar masses and shines as much as 5000 very bright massive stars. It may well be very similar to the progenitors in the early Universe of the old globular clusters we now observe in large galaxies like the Milky Way. In this sense, NGC 5253 provides us with a direct view towards our own beginnings. Note [1] The group consists of Giovanni Cresci (University of Florence, Italy), Leonardo Vanzi (ESO-Chile) and Marc Sauvage (CEA/DSN/DAPNIA, Saclay, France). More details about the present investigation is available in a research paper ("The Star Cluster population of NGC 5253" by G. Cresci et al.) to appear soon in the leading research journal Astronomy & Astrophysics (a preprint is available as astro-ph/0411486). Original Source: ESO News Release http://www.universetoday.com/am/publish/blue_dwarf_galaxy_cluster.html?18112004

It's a Galaxy Eat Galaxy Universe Summary - (Nov 19, 2004) Japanese researchers using the Subaru Telescope have found a large galaxy caught in the act of consuming a smaller companion galaxy. It's a messy eater; there's a wispy trail of stars over 500,000 light-years long, which is the longest astronomers have ever seen. Examples of this kind of galactic destruction are hard to find because the consumed are usually dim dwarf galaxies. We have only indirect evidence of digested galaxies in our own Milky Way, like groups of stars traveling in an unusual trajectory. Full Story - Subaru telescope has witnessed a large galaxy in the act of devouring a small companion galaxy in a new image obtained by Yoshiaki Taniguchi (Tohoku University), Shunji Sasaki (Tohoku University), Nicolas Scoville (California Institute of Technology) and colleagues. The evidence is a wispy band of stars extending over 500 thousand light years, the faintest and longest known example of its kind. Current theories of galaxy formation suggest that large galaxies like the Milky Way grow by consuming smaller dwarf galaxies. Evidence of this process can be found in our own galactic neighborhood. Some stars in the Milky Way appear to have once belonged to a small nearby galaxy called the Sagitarius Dwarf. Our closest large neighbor galaxy Andromeda also shows evidence for past galactic astronomy. However, in both cases these conclusions are inferred from "post-digestive" observations. The destruction of dwarf galaxies is difficult to observe because dwarf galaxies are inherently faint and their light becomes increasingly diffuse as stars get pulled away by a larger galaxy. The only previously known observation of the destruction of a dwarf galaxy in progress is from the Advanced Camera for Surveys on the Hubble Space Telescope. Taniguchi, Sasaki, Scoville and colleagues serendipitously discovered the large elliptical galaxy (COSMOS J100003+020146) pulling apart the dwarf galaxy (COSMOS J095959+020206) while observing an area of sky in the constellation Sextans to study the properties of galaxies over large scales in space and time. The pair of galaxies is about one billion light years away and the distance between the two galaxies is about 330 thousand light years. The thin band of stars extending from the dwarf galaxy both toward and away from the large elliptical galaxy reveals that the gravity of the elliptical is tidally tearing the dwarf apart. Stars that are closest to the elliptical galaxy experience a stronger pull than stars in the center of the dwarf galaxy, and stars on the opposite side experience a weaker pull. As a result, the dwarf galaxy becomes stretched and looks as if it's being pulled from two opposite directions even though there is only one galaxy doing the pulling. This effect is comparable to how two areas on the opposite sides of Earth experience high tide at the same time even though there is only one Moon tugging on Earth's oceans. The tidally torn strip of stars in the newly observed pair of galaxies is five times more extended and three times fainter in surface brightness than the one observed with Hubble Space Telescope. Subaru telescope's ability to gather large amounts of light and focus it into a superbly sharp image was essential for this new discovery. As astronomers find more examples of galactic cannibalism in action, our knowledge of the history of galaxies should become increasingly vivid. Although no human alive today will be able to witness the ultimate of fate of the newly discovered pair, chances are the elliptical galaxy will be able to complete the meal it's begun and fully consume its neighbor. Original Source: Subaru News Release http://www.universetoday.com/am/publish/galaxy_eat_galaxy.html?19112004

PRESS RELEASE Date Released: Wednesday, December 01, 2004 Source: European Southern Observatory Explosions in Majestic Spiral Beauties Very Large Telescope Takes Snapshots of Two Grand-Design Spiral Galaxies Images of beautiful galaxies, and in particular of spiral brethren of our own Milky Way, leave no-one unmoved. It is difficult indeed to resist the charm of these impressive grand structures. Astronomers at Paranal Observatory used the versatile VIMOS instrument on the Very Large Telescope to photograph two magnificent examples of such "island universes", both of which are seen in a southern constellation with an animal name. But more significantly, both galaxies harboured a particular type of supernova, the explosion of a massive star during a late and fatal evolutionary stage. The first image (PR Photo 33a/04) is of the impressive spiral galaxy NGC 6118 [1], located near the celestial equator, in the constellation Serpens (The Snake). It is a comparatively faint object of 13th magnitude with a rather low surface brightness, making it pretty hard to see in small telescopes. This shyness has prompted amateur astronomers to nickname NGC 6118 the "Blinking Galaxy" as it would appear to flick into existence when viewed through their telescopes in a certain orientation, and then suddenly disappear again as the eye position shifted. There is of course no such problem for the VLT's enormous light-collecting power and ability to produce sharp images, and this magnificent galaxy is here seen in unequalled detail. The colour photo is based on a series of exposures behind different optical filters, obtained with the VIMOS multi-mode instrument on the 8.2-m VLT Melipal telescope during several nights around August 21, 2004. About 80 million light-years away, NGC 6118 is a grand-design spiral seen at an angle, with a very small central bar and several rather tightly wound spiral arms (it is classified as of type "SA(s)cd" [2]) in which large numbers of bright bluish knots are visible. Most of them are active star-forming regions and in some, very luminous and young stars can be perceived. Of particular interest is the comparatively bright stellar-like object situated directly North of the galaxy's centre, near the periphery (see PR Photo 33b/04): it is Supernova 2004dk that was first reported on August 1, 2004. Observations a few days later showed this to be a supernova of Type Ib or Ic [3] , caught a few days before maximum light. This particular kind of supernova is believed to result from the demise of a massive star that has somehow lost its entire hydrogen envelope, probably as a result of mass transfer in a binary system, before exploding. Also visible on the image is the trail left by a satellite, which passed by during one of the exposures taken in the B filter, hence its blue colour. This is an illustration that even in such a remote place as the Paranal Observatory in the Atacama desert, astronomers are not completely sheltered from light pollution. The second galaxy imaged by the VLT (ESO PR Photo 33c/04) is another spiral, the beautiful multi-armed NGC 7424 that is seen almost directly face-on. Located at a distance of roughly 40 million light-years in the constellation Grus (the Crane), this galaxy was discovered by Sir John Herschel while observing at the Cape of Good Hope. This other example of a "grand design" galaxy is classified as "SAB(rs)cd" [2], meaning that it is intermediate between normal spirals (SA) and strongly barred galaxies (SB) and that it has rather open arms with a small central region. It also shows many ionised regions as well as clusters of young and massive stars. Ten young massive star clusters can be identified whose sizes span the range from 1 to 200 light-years. The galaxy itself is roughly 100,000 light-years across, that is, quite similar in size to our own Milky Way galaxy. Because of its low surface brightness, this galaxy also demands dark skies and a clear night to be observed in this impressive detail. When viewed in a small telescope, it appears as a large elliptical haze with no trace of the many beautiful filamentary arms with a multitude of branches revealed in this striking VLT image. Note also the very bright and prominent bar in the middle. On the evening of 10 December 2001, Australian amateur astronomer Reverend Robert Evans, observing from his backyard in the Blue Mountains west of Sydney, discovered with his 30cm telescope his 39th supernova, Supernova 2001ig in the outskirts of NGC 7424. Of magnitude 14.5 (that is, 3000 times fainter than the faintest star that can be seen with the unaided eye), this supernova brightened quickly by a factor 8 to magnitude 12.3. A few months later, it had faded to an insignificant object below 17th magnitude. By comparison, the entire galaxy is of magnitude 11: at the time of its maximum, the supernova was thus only three times fainter than the whole galaxy. It must have been a splendid firework indeed! By digging into the vast Science Archive of the ESO Very Large Telescope, it was possible to find an image of NGC 7424 taken on June 16, 2002 by Massimo Turatto (Observatorio di Padova-INAF, Italy) with the FORS 2 instrument on Yepun (UT4). Although, the supernova was already much fainter than at its maximum 6 months earlier, it is still very well visible on this image (see PR Photo 33d/04). Spectra taken with ESO's 3.6-m telescope at La Silla over the months following the explosion showed the object to evolve to a Type Ib/c supernova. By October 2002, the transition to a Type Ib/c supernova was complete. It is now believed that this supernova arose from the explosion of a very massive star, a so-called Wolf-Rayet star, which together with a massive hot companion belonged to a very close binary system in which the two stars orbited each other once every 100 days or so. Future detailed observations may reveal the presence of the companion star that survived this explosion but which is now doomed to explode as another supernova in due time. The full text of this ESO PR Photo Release, with four images and all weblinks, is available at: http://www.eso.org/outreach/press-rel/pr-2004/phot-33-04.html Notes [1] NGC stands for "New General Catalogue". Published in 1888 by J.L.E. Dreyer, this New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel contains 7840 objects of which 3200 are galaxies. [2] Spiral galaxies take their name from the spectacular spiral arms that wind around in a very thin disc. Following the celebrated classification by American astronomer Edwin Hubble, spiral galaxies are classified into two families, so-called normal spirals (SA) and barred spirals (SB), and are further divided into types Sa, Sb and Sc depending on the opening of the spiral arms and the relative brightness of the central area. In barred spiral galaxies, the nucleus is crossed by a bar of stars at the ends of which the spiral arms begin. The (rs) in the classification testifies to the presence of an internal ring (r) surrounding the nucleus of the galaxy as well as to the fact that the spiral arms begin directly at the nucleus (s). [3] Supernovae are classified into different types, depending on the appearance of their spectrum. Type II supernovae show the presence of hydrogen lines in their spectra while Type I lack this signature. Type I have been subdivided into Type Ia, Ib and Ic. Type I supernovae are all believed to arise in binary stellar systems. http://www.spaceref.com/news/viewpr.html?pid=15585

PRESS RELEASE Date Released: Wednesday, December 01, 2004 Source: Space Telescope Science Institute Astronomers Uncover a Baby Galaxy in a Grown-Up Universe Scientists using NASA's Hubble Space Telescope have measured the age of what may be the youngest galaxy ever seen in the universe. By cosmological standards it is a mere toddler seemingly out of place among the grown-up galaxies around it. Called I Zwicky 18, it may be as young as 500 million years old (so recent an epoch that complex life had already begun to appear on Earth). Our Milky Way galaxy by contrast is over 20 times older, or about 12 billion years old, the typical age of galaxies across the universe. This "late-life" galaxy offers a rare glimpse into what the first diminutive galaxies in the early universe look like. The galaxy is a member of a catalog of 30,000 nearby galaxies that Swiss astronomer Fred Zwicky assembled in the 1930's by photographing the entire northern sky. Though astronomers have long suspected that this galaxy was a youngster, due to its primordial chemical makeup, Hubble's exquisite sensitivity allowed astronomers to do a reliable census of the total stellar population in the galaxy. This allowed them to reliably identify the oldest stars inhabiting the galaxy, thereby setting an upper limit on the galaxy's age. The baby galaxy managed to remain in an embryonic state as a cold gas cloud of primeval hydrogen and helium for most of the duration of the universe's evolution. As innumerable galaxies blossomed all over space this late-bloomer did not begin active star formation until some 13 billion years after the Big Bang, and went through a sudden first starburst only some 500 million years ago. Located only 45 million light-years away -- much closer than other young galaxies in the nearly 14 billion light-year span of the universe -- I Zwicky 18 might represent the only opportunity for astronomers to study in detail the building blocks from which galaxies are formed. It remains a puzzle why the gas in the dwarf galaxy, in contrast to that in other galaxies, took so long -- nearly the age of the universe -- to collapse under the influence of gravity to form its first stars. "I Zwicky 18 is a bona fide young galaxy," said Trinh Thuan, professor of astronomy at the University of Virginia, who co-authored the study with Yuri Izotov from the Kiev Observatory. "This is extraordinary because one would expect young galaxies to be forming only around the first billion years or so after the Big Bang, not some 13 billion years later. And young galaxies were expected to be very distant, at the edge of the observable universe, but not in the local universe," Izotov said. The finding, reported in the December 1 issue of the Astrophysical Journal, provides a new insight into how galaxies first formed. The galaxy I Zwicky 18 offers a glimpse of what the early Milky Way may have looked like 13 billion years ago. Another set of Hubble observations by a different team give a slightly older age of 1 billion years to the galaxy, still keeping it a comparative newborn. Goran Ostlin of Stockholm Observatory, and Mustapha Mouhcine of the University of Nottingham, used Hubble's Near Infrared Camera and Multi-Object Spectrometer to find a population of cool red stars, which are slightly older than the stars seen by the Advanced Camera for Surveys Camera. The results are to be published in Astronomy & Astrophysics. To prove that I Zwicky 18 is a new galaxy, Thuan and Izotov needed to show that it was devoid of stars from the first several billion years after the Big Bang, the period when a large fraction of stars in the universe were formed. Though astronomers had suspected that the galaxy was exceptionally young, they had to wait for Hubble to provide the needed sensitivity to detect whether or not older stars, faint red giants, existed within the dwarf galaxy. Hubble's Advanced Camera for Surveys needed a very long exposure, requiring 25 telescope orbits to look for the faintest stars in the galaxy. The presence of old stars in the galaxy would have indicated that the galaxy itself was old, like all other known galaxies in the universe. Large galaxies such as the Milky Way are thought to grow hierarchically, with smaller galaxies merging into bigger galaxies, like tributaries merging into large rivers. I Zwicky 18 is prototypical of this early population of small dwarf galaxies. "These building block dwarf galaxies are too faint and too small to be studied without the most sensitive instruments even in the local universe, let alone in the far reaches of the cosmos," Thuan said. Further evidence for the youth of I Zwicky 18 is the fact that its interstellar gas is "nearly pristine," Thuan said, and composed mostly of hydrogen and helium, the primary two light elements created in the Big Bang, during the first three minutes of the universe's existence. The dwarf galaxy includes only a sprinkling of the other heavier elements such as carbon, nitrogen, or oxygen that are created later as stars develop. The near absence of such heavy elements suggests that much of the primordial gas in the dwarf galaxy has not managed to form stars that subsequently manufacture heavy elements. Electronic images and additional information are available at: http://hubblesite.org/news/2004/35 For more information, please contact: Trinh Thuan, University of Virginia, Department of Astronomy, Box 38918, Univ. Station, Charlottesville, VA 22903-0818, (phone) 434-924-4894,(e-mail) [email protected] Goran Ostlin, Stockholm Observatory, Institute for Astronomy, AlbaNova, SCFAB, Roslagstullsbacken 21, SE-106 91 Stockholm, Sweden, (phone) +46-8-5537-8513, (e-mail) [email protected] The Space Telescope Science Institute (STScI) is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), for NASA, under contract with the Goddard Space Flight Center, Greenbelt, MD. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA). http://www.spaceref.com/news/viewpr.html?pid=15586

Youngest Galaxy Found Summary - (Dec 1, 2004) The Hubble Space Telescope has helped astronomers discover the youngest known galaxy in the Universe. This baby galaxy, located 45 million light-years away seems to be only 500 million years old (our own Milky Way galaxy, like many galaxies in the Universe is 12 billion years old). Its interstellar gas is "nearly pristine", comprised mainly of hydrogen and helium, with only a sprinkling of the heavier elements associated with older galaxies. This discovery gives astronomers an opportunity to understand how galaxies first formed. Full Story - Scientists using NASA's Hubble Space Telescope have measured the age of what may be the youngest galaxy ever seen in the universe. By cosmological standards it is a mere toddler seemingly out of place among the grown-up galaxies around it. Called I Zwicky 18, it may be as young as 500 million years old (so recent an epoch that complex life had already begun to appear on Earth). Our Milky Way galaxy by contrast is over 20 times older, or about 12 billion years old, the typical age of galaxies across the universe. This "late-life" galaxy offers a rare glimpse into what the first diminutive galaxies in the early universe look like. The galaxy is a member of a catalog of 30,000 nearby galaxies that Swiss astronomer Fred Zwicky assembled in the 1930's by photographing the entire northern sky. Though astronomers have long suspected that this galaxy was a youngster, due to its primordial chemical makeup, Hubble's exquisite sensitivity allowed astronomers to do a reliable census of the total stellar population in the galaxy. This allowed them to reliably identify the oldest stars inhabiting the galaxy, thereby setting an upper limit on the galaxy's age. The baby galaxy managed to remain in an embryonic state as a cold gas cloud of primeval hydrogen and helium for most of the duration of the universe's evolution. As innumerable galaxies blossomed all over space this late-bloomer did not begin active star formation until some 13 billion years after the Big Bang, and went through a sudden first starburst only some 500 million years ago. Located only 45 million light-years away — much closer than other young galaxies in the nearly 14 billion light-year span of the universe — I Zwicky 18 might represent the only opportunity for astronomers to study in detail the building blocks from which galaxies are formed. It remains a puzzle why the gas in the dwarf galaxy, in contrast to that in other galaxies, took so long — nearly the age of the universe — to collapse under the influence of gravity to form its first stars. "I Zwicky 18 is a bona fide young galaxy," said Trinh Thuan, professor of astronomy at the University of Virginia, who co-authored the study with Yuri Izotov from the Kiev Observatory. "This is extraordinary because one would expect young galaxies to be forming only around the first billion years or so after the Big Bang, not some 13 billion years later. And young galaxies were expected to be very distant, at the edge of the observable universe, but not in the local universe," Izotov said. The finding, reported in the December 1 issue of the Astrophysical Journal, provides a new insight into how galaxies first formed. The galaxy I Zwicky 18 offers a glimpse of what the early Milky Way may have looked like 13 billion years ago. Another set of Hubble observations by a different team give a slightly older age of 1 billion years to the galaxy, still keeping it a comparative newborn. Goran Ostlin of Stockholm Observatory, and Mustapha Mouhcine of the University of Nottingham, used Hubble's Near Infrared Camera and Multi-Object Spectrometer to find a population of cool red stars, which are slightly older than the stars seen by the Advanced Camera for Surveys Camera. The results are to be published in Astronomy & Astrophysics. To prove that I Zwicky 18 is a new galaxy, Thuan and Izotov needed to show that it was devoid of stars from the first several billion years after the Big Bang, the period when a large fraction of stars in the universe were formed. Though astronomers had suspected that the galaxy was exceptionally young, they had to wait for Hubble to provide the needed sensitivity to detect whether or not older stars, faint red giants, existed within the dwarf galaxy. Hubble's Advanced Camera for Surveys needed a very long exposure, requiring 25 telescope orbits to look for the faintest stars in the galaxy. The presence of old stars in the galaxy would have indicated that the galaxy itself was old, like all other known galaxies in the universe. Large galaxies such as the Milky Way are thought to grow hierarchically, with smaller galaxies merging into bigger galaxies, like tributaries merging into large rivers. I Zwicky 18 is prototypical of this early population of small dwarf galaxies. "These building block dwarf galaxies are too faint and too small to be studied without the most sensitive instruments even in the local universe, let alone in the far reaches of the cosmos," Thuan said. Further evidence for the youth of I Zwicky 18 is the fact that its interstellar gas is "nearly pristine," Thuan said, and composed mostly of hydrogen and helium, the primary two light elements created in the Big Bang, during the first three minutes of the universe's existence. The dwarf galaxy includes only a sprinkling of the other heavier elements such as carbon, nitrogen, or oxygen that are created later as stars develop. The near absence of such heavy elements suggests that much of the primordial gas in the dwarf galaxy has not managed to form stars that subsequently manufacture heavy elements. Original Source: Hubble News Release http://www.universetoday.com/am/publish/youngest_galaxy_found.html?1122004

Supernova in a Distant Galaxy NGC 6118 Summary - (Dec 1, 2004) Astronomers at the European Southern Observatory's Paranal Observatory took this image of galaxy NGC 6118, located 80 million light-years away. A supernova was discovered exploding just north of the galaxy's centre on August 1, 2004. Astronomers now believe that it is a Type 1b or 1c, which means that it probably arose in a binary star system; a massive star whose hydrogen envelope was siphoned off by its stellar partner before it exploded. Full Story - Images of beautiful galaxies, and in particular of spiral brethren of our own Milky Way, leaves no-one unmoved. It is difficult indeed to resist the charm of these impressive grand structures. Astronomers at Paranal Observatory used the versatile VIMOS instrument on the Very Large Telescope to photograph two magnificent examples of such "island universes", both of which are seen in a southern constellation with an animal name. But more significantly, both galaxies harboured a particular type of supernova, the explosion of a massive star during a late and fatal evolutionary stage. This image is of the impressive spiral galaxy NGC 6118 [1], located near the celestial equator, in the constellation Serpens (The Snake). It is a comparatively faint object of 13th magnitude with a rather low surface brightness, making it pretty hard to see in small telescopes. This shyness has prompted amateur astronomers to nickname NGC 6118 the "Blinking Galaxy" as it would appear to flick into existence when viewed through their telescopes in a certain orientation, and then suddenly disappear again as the eye position shifted. There is of course no such problem for the VLT's enormous light-collecting power and ability to produce sharp images, and this magnificent galaxy is here seen in unequalled detail. The colour photo is based on a series of exposures behind different optical filters, obtained with the VIMOS multi-mode instrument on the 8.2-m VLT Melipal telescope during several nights around August 21, 2004. About 80 million light-years away, NGC 6118 is a grand-design spiral seen at an angle, with a very small central bar and several rather tightly wound spiral arms (it is classified as of type "SA(s)cd" [2]) in which large numbers of bright bluish knots are visible. Most of them are active star-forming regions and in some, very luminous and young stars can be perceived. Of particular interest is the comparatively bright stellar-like object situated directly North of the galaxy's centre, near the periphery (see PR Photo 33b/04): it is Supernova 2004dk that was first reported on August 1, 2004. Observations a few days later showed this to be a supernova of Type Ib or Ic [3], caught a few days before maximum light. This particular kind of supernova is believed to result from the demise of a massive star that has somehow lost its entire hydrogen envelope, probably as a result of mass transfer in a binary system, before exploding. Also visible on the image is the trail left by a satellite, which passed by during one of the exposures taken in the B filter, hence its blue colour. This is an illustration that even in such a remote place as the Paranal Observatory in the Atacama desert, astronomers are not completely sheltered from light pollution. The second galaxy imaged by the VLT is another spiral, the beautiful multi-armed NGC 7424 that is seen almost directly face-on. Located at a distance of roughly 40 million light-years in the constellation Grus (the Crane), this galaxy was discovered by Sir John Herschel while observing at the Cape of Good Hope. This other example of a "grand design" galaxy is classified as "SAB(rs)cd" [2], meaning that it is intermediate between normal spirals (SA) and strongly barred galaxies (SB) and that it has rather open arms with a small central region. It also shows many ionised regions as well as clusters of young and massive stars. Ten young massive star clusters can be identified whose size span the range from 1 to 200 light-years. The galaxy itself is roughly 100,000 light-years across, that is, quite similar in size to our own Milky Way galaxy. Because of its low surface brightness, this galaxy also demands dark skies and a clear night to be observed in this impressive detail. When viewed in a small telescope, it appears as a large elliptical haze with no trace of the many beautiful filamentary arms with a multitude of branches revealed in this striking VLT image. Note also the very bright and prominent bar in the middle. On the evening of 10 December 2001, Australian amateur astronomer Reverend Robert Evans, observing from his backyard in the Blue Mountains west of Sydney, discovered with his 30cm telescope his 39th supernova, Supernova 2001ig in the outskirts of NGC 7424. Of magnitude 14.5 (that is, 3000 times fainter than the faintest star that can be seen with the unaided eye), this supernova brightened quickly by a factor 8 to magnitude 12.3. A few months later, it had faded to an insignificant object below 17th magnitude. By comparison, the entire galaxy is of magnitude 11: at the time of its maximum, the supernova was thus only three times fainter than the whole galaxy. It must have been a splendid firework indeed! By digging into the vast Science Archive of the ESO Very Large Telescope, it was possible to find an image of NGC 7424 taken on June 16, 2002 by Massimo Turatto (Observatorio di Padova-INAF, Italy) with the FORS 2 instrument on Yepun (UT4). Although, the supernova was already much fainter than at its maximum 6 months earlier, it is still very well visible on this image (see PR Photo 33d/04). Spectra taken with ESO's 3.6-m telescope at La Silla over the months following the explosion showed the object to evolve to a Type Ib/c supernova. By October 2002, the transition to a Type Ib/c supernova was complete. It is now believed that this supernova arose from the explosion of a very massive star, a so-called Wolf-Rayet star, which together with a massive hot companion belonged to a very close binary system in which the two stars orbited each other once every 100 days or so. Future detailed observations may reveal the presence of the companion star that survived this explosion but which is now doomed to explode as another supernova in due time. [1] NGC stands for "New General Catalogue". Published in 1888 by J.L.E. Dreyer, this New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel contains 7840 objects of which 3200 are galaxies. [2] Spiral galaxies take their name from the spectacular spiral arms that wind around in a very thin disc. Following the celebrated classification by American astronomer Edwin Hubble, spiral galaxies are classified into two families, so-called normal spirals (SA) and barred spirals (SB), and are further divided into types Sa, Sb and Sc depending on the opening of the spiral arms and the relative brightness of the central area. In barred spiral galaxies, the nucleus is crossed by a bar of stars at the ends of which the spiral arms begin. The (rs) in the classification testifies to the presence of an internal ring (r) surrounding the nucleus of the galaxy as well as to the fact that the spiral arms begin directly at the nucleus (s). [3] Supernovae are classified into different types, depending on the appearance of their spectrum. Type II supernovae show the presence of hydrogen lines in their spectra while Type I lack this signature. Type I have been subdivided into Type Ia, Ib and Ic. Type I supernovae are all believed to arise in binary stellar systems. Original Source: ESO News Release http://www.universetoday.com/am/publish/supernova_ngc_6118.html?1122004

Sun Could Have Traded With Another Star Summary - (Dec 2, 2004) Astronomers from the Harvard-Smithsonian Center for Astrophysics believe it's possible that our own Sun could have stolen some material from other stars billions of years ago. They came to this conclusion while trying to understand the orbit of Sedna, which takes 10,000 years to go around the Sun, in a highly elliptical orbit far beyond the Kuiper Belt. When our Sun was younger than 200 million years old, it could have swept past another star, disrupting the Kuiper Belt, and trading large objects (like Sedna) with each other. Full Story - A hit TV program like "Antiques Roadshow" lures viewers with its universal appeal. Who wouldn't want to find secret riches in their attic or basement? But rare paintings and heirloom jewelry aren't the only valuable items waiting to be discovered. Cosmic treasures also lay hidden in the vast realm of outer space. Among the most highly prized of those treasures are planets that formed around other stars. Astronomers have just gained an important clue to guide their hunt for extrasolar worlds. And that clue points to the unlikeliest of places - our own backyard. "It's possible that some of the objects in our solar system actually formed around another star," says astronomer Scott Kenyon (Smithsonian Astrophysical Observatory). How did these adopted worlds join our solar family? They arrived through an interstellar trade that took place more than 4 billion years ago when a wayward star brushed past our solar system. According to calculations made by Kenyon and astronomer Benjamin Bromley (University of Utah) and published in the Dec. 2, 2004, Nature, the Sun's gravity plucked asteroid-sized objects from the visiting star. At the same time, the star pulled material from the outer reaches of our solar system into its grasp. "There may not have been an equal exchange, but there was certainly an exchange," says Bromley. A Close Brush Kenyon and Bromley reached this surprising conclusion while working to explain the mystery object Sedna, a world almost as large as Pluto but located much farther from the Sun. Sedna's discovery in 2003 puzzled astronomers because of its unusual orbit - a 10,000-year-long oval whose closest approach to the Sun, 70 astronomical units, is well beyond the orbit of Neptune. (One astronomical unit, abbreviated A.U., is the average distance between the Earth and the Sun, or about 93 million miles.) Understanding Sedna is a challenge because its orbit is far away from the gravitational influence of other planets in our solar system. However, the gravity of a passing star can pull objects beyond the orbit of Neptune, in the Kuiper Belt, into orbits like Sedna's. Kenyon and Bromley have performed detailed computer simulations to show how this stellar fly-by likely took place. The fly-by must have met two key requirements. First, the star must have stayed far enough away that it did not disrupt Neptune's nearly circular orbit. Second, the encounter must have happened late enough in our solar system's history that Sedna-like objects had time to form within the Kuiper Belt. Kenyon and Bromley suggest that the near-collision occurred when our Sun was at least 30 million years old, and probably no more than 200 million years old. A fly-by distance of 150-200 A.U. would be close enough to disrupt the outer Kuiper Belt without affecting the inner planets. According to the simulations, the passing star's gravity would sweep clear the outer solar system beyond about 50 A.U., even as our Sun's gravity pulled some of the alien planetoids into its grasp. The model explains both the orbit of Sedna and the observed sharp outer edge of our Kuiper Belt, where few objects reside beyond 50 A.U. "A close fly-by from another star solves two mysteries at once. It explains both the orbit of Sedna and the outer edge of the Kuiper Belt," says Bromley. A Crowded Birthplace But where did such a star come from, and where did it go? Since the fly-by happened more than 4 billion years ago, any suspects have long since escaped the Sun's neighborhood. There is no practical way to find the culprit today. The visitor's origin may seem equally mystifying because the Sun currently lives in a sparse region of the Milky Way. Our closest neighbor is a distant 4 light-years away, and stellar close encounters are correspondingly rare. However, a near-collision would be much more likely for a young Sun if it were born in a dense star cluster, as recent evidence suggests. "We believe that 90 percent of all stars form in clusters with a few hundred to a few thousand members," says astronomer Charles Lada (Harvard-Smithsonian Center for Astrophysics). "The denser the cluster, the more likely the chance for an encounter between member stars." "This work is an important piece of evidence that the Sun formed in near proximity to other stars," he adds. Searching for Adopted Worlds Kenyon and Bromley's simulations indicate that thousands or possibly millions of alien Kuiper Belt Objects were stripped from the passing star. However, none have yet been positively identified. Sedna is probably homegrown, not captured. Among the known Kuiper Belt Objects, an icy rock dubbed 2000 CR105 is the best candidate for capture given its unusually elliptical and highly inclined orbit. But only the detection of objects with orbits inclined more than 40 degrees from the plane of the solar system will clinch the case for the presence of extrasolar planets in our backyard. Kenyon and Bromley's next goal is to estimate the sky density of captured objects so that they can make a survey to find such adopted worlds. "In principle, large telescopes like the MMT Telescope [a joint Smithsonian/University of Arizona observatory] can find them if they're numerous enough," says Kenyon. The calculations reported here were made using about 3,000 cpu-days of computer time at the supercomputing center at the Jet Propulsion Laboratory, Pasadena, Calif. Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe. Original Source: Harvard CfA News Release http://www.universetoday.com/am/publish/sun_material_collector.html?2122004

Dusty Universe is a Mystery Summary - (Dec 2, 2004) The early Universe was much dustier than astronomers were expecting, according to new data gathered by the Spitzer Space Telescope. This leads to the question, how did it get so dusty so early? Regular stars take billions of years before they star giving off large amounts of dust. But massive stars can form quickly and then explode as supernovae within 10 million years. The problem is that these explosions produce enormous amounts of hot dust, but very little cold dust, which is the kind found in the early Universe. So, the mystery continues. Full Story - Image credit: NASA/JPL/UA Astronomers who think they know how the very early universe came to have so much interstellar dust need to think again, according to new results from the Spitzer Space Telescope. In the last few years, observers have discovered huge quantities of interstellar dust near the most distant quasars in the very young universe, only 700 million years after the cosmos was born in the Big Bang. "And that becomes a big question," said Oliver Krause of the University of Arizona Steward Observatory in Tucson and the Max Planck Institute for Astronomy in Heidelberg. "How could all of this dust have formed so quickly?" Astronomers know two processes that form the dust, Krause said. One, old sun-like stars near death generate dust. Two, infrared space missions have revealed the dust is produced in supernovae explosions. "The first process takes several billion years," Krause noted. "Supernovae explosions, by contrast, produce dust in much less time, only about 10 million years." So when astronomers reported detecting submillimeter emission from massive amounts of cold interstellar dust in the supernova remnant Cassiopeia A last year, some considered the mystery solved. Type II supernovae like 'Cas A' likely produced the interstellar dust in the very early universe, they concluded. (Type II supernovae come from massive stars that blow apart in huge explosions after their cores collapse.) Krause and colleagues from UA's Steward Observatory and the Max Planck institute in Heidelberg have now discovered that the detected submillimeter emission comes not from the Cas A remnant itself but from the molecular cloud complex known to exist along the line of sight between Earth and Cas A. They report the work in the Dec. 2 issue of Nature. Cas A is the youngest known supernova remnant in our Milky Way. It is about 11,000 light years away, behind the Perseus spiral arm clouds that are roughly 9,800 light years away. Krause suspects that the Perseus clouds explain why late 17th century astronomers didn't report observing the brilliant Cas A outburst around A.D. 1680. Cas A is so close to Earth that the supernova should have been the brightest stellar object in the sky, but dust in the Perseus clouds eclipsed the view. The Arizona and German team mapped Cas A at 160-micron wavelengths using the ultra-heat-sensitive Multiband Imaging Photometer (MIPS) aboard the Spitzer Space Telescope. These long wavelengths are the most sensitive to cold interstellar dust emission. They then compared the results with maps of interstellar gas previously made with radio telescopes. They found that the dust in these interstellar clouds account for virtually all the emission at 160 microns from the direction of Cas A. Minus the emission from this dust, there is no evidence for large amounts of cold dust in Cas A, the team concludes. "Astronomers will have to go on searching for the source of the dust in the early universe," UA Steward Observatory astronomer and Regents' Professor George Rieke said. Rieke is principal investigator for the Spitzer Space Telescope's MIPS instrument and a co-author of the Nature paper. "Solving this riddle will show astronomers where and how the first stars formed, or perhaps indicate there is some non-stellar process that can produce large amounts of dust," Rieke said. "Either way, (finding the source of the dust) will reveal what went on at the formative stage for stars and galaxies, an epoch that is nearly unobserved in any other way." Authors of the Nature article, "No cold dust within the supernova remnant Cassiopeia A," are Oliver Krause, Stephan M. Birkmann, George H. Rieke, Dietrich Lemke, Ulrich Klaas, Dean C. Hines and Karl D. Gordon. Birkmann, Lemke and Klaas are with the Max Planck Institute for Astronomy in Heidelberg. Krause, Rieke, and Gordon are with the University of Arizona Steward Observatory. Hines is with the Space Science Institute in Boulder, Colo. Original Source: UA News Release http://www.universetoday.com/am/publish/dusty_universe_mystery.html?2122004

LUZ VERDE AL CONVENIO Fecha Jueves, 07 octubre a las 10:00:00 Tema Sociedad Aprobado un nuevo trámite para facilitar la instalación de una antena espacial en Cebreros. La Comisión de Asuntos Exteriores del Congreso de los Diputados ha propuesto al Pleno de la Cámara que conceda la autorización solicitada por el Gobierno para ratificar el acuerdo entre el Reino de España y la Agencia Espacial Europea que prevé el establecimiento de instalaciones de seguimiento terrestre y adquisición de datos, incluida una antena de espacio lejano en Cebreros. Las misiones de investigación espacial de la futura estación de seguimiento de Cebreros permitirán reforzar el papel de la Agencia Espacial Europea en España, puesto que este municipio se sitúa en un entorno considerado adecuado al no existir perturbaciones radioeléctricas. La antena de Cebreros, junto con las ya existentes en Villafranca del Castillo y Robledo de Chavela, ambas en Madrid, será también una valiosa contribución al marco científico y tecnológico de las actividades espaciales europeas, ya que trabajará a las frecuencias más altas empleadas nunca para el seguimiento de satélites científicos. http://www.avilared.com/modules.php?name=AvantGo&file=print&sid=6152

El Sistema Solar también tiene un escudo deflector Si alguna vez has visto Star Trek, entonces sabes la importancia que tienen los escudos. Cuando una estrella explota o un Klingon lanza sus mortíferos rayos en la oscuridad, el capitán grita dos palabras "¡Activar escudos!", y todo va bien. Escudos deflectores: no salgas de casa sin uno. El Sistema Solar, lo creas o no, tiene uno. 10:06 - 11/10/2004 | Fuente: ASTROSETI El escudo deflector del Sistema Solar es una gran burbuja magnética llamada "heliósfera". Es parte del campo magnético del Sol. Nadie sabe las dimensiones exactas de la heliósfera, pero es más grande que la órbita de Plutón. Los nueve planetas están dentro de ella. La heliósfera es importante para la vida en nuestro planeta. Hace unos pocos millones de años, por ejemplo, un grupo de estrellas masivas fluctuaban a través de nuestra parte de la Vía Láctea y explotaron una después de la otra, como palomitas de maíz. Los rayos cósmicos de la explosión fueron en su mayor parte desviados evitando un baño de radiación sobre los primeros humanos. Pero la burbuja no es perfecta. El hecho es que "está resquebrajada" dice el científico espacial Eberhard Moebius de la Universidad de New Hampshire. "Esas cosas pasan". (Esto también sucede en Star Trek. Si los escudos de la nave fueran impenetrables, nunca habría ningún drama). Toma los rayos cósmicos, como ejemplo. Son fragmentos de átomos estrellados y acelerados a la velocidad de la luz por las explosiones de supernovas. La heliósfera desvía cerca de un 90% de estos, el resto, el 10% de los más poderosos, penetran en el interior del Sistema Solar. La burbuja es incluso más vulnerable para partículas sin carga eléctrica. Los campos Magnéticos pueden desviar partículas cargadas como los rayos cósmicos, pero no los átomos y moléculas neutras o trozos de polvo y roca. La burbuja es una puerta abierta para éstos. A saber: un flujo de átomos neutros de helio – "una brisa interestelar", dice Moebius—está fluyendo ahora mismo hacia el interior del Sistema Solar. "Su dirección proviene de la constelación de Sagitario. Como los átomos del flujo no están cargados, la burbuja magnética no hace nada para detenerlos". Estudiar este flujo es importante porque puede enseñarnos mucho sobre la heliósfera— ¿Qué tan grande es?, ¿Cuán resquebrajada está? También puede enseñarnos sobre la "materia" interestelar escondida ahí fuera", dice Moebius. El flujo, descubierto hace 30 años, es controlado activamente por una flotilla de la NASA y una nave espacial de la Agencia Espacial Europea: SOHO, EUVE, ACE y, especialmente Ulises. Cada una mide algo diferente. EUVE, por ejemplo, puede percibir la luz del Sol ultravioleta dispersa en el flujo, mientras la Ulises toma muestras del propio flujo, recogiendo átomos directamente de él. Durante muchos años las características físicas del flujo sólo eran vagamente conocidas. "Pero la capacidad que tenemos ahora para observar la corriente con detalle usando estas modernas naves es lo que marca la diferencia" dice Moebius. Recientemente dirigió un equipo de investigación en el International Space Science Institute (Instituto Internacional de la Ciencia del Espacio) en Suiza; empleando datos de estas naves, fueron capaces de precisar la temperatura del flujo, densidad y velocidad: Su temperatura, 6000 ºC, es más o menos la misma que la existente en la superficie del Sol. Una nave espacial volando a través del flujo no se fundirá, ni siquiera notará el calor. El gas en el flujo es tenue y fino, explica Moebius. "Sólo hay 0.015 átomos de helio por centímetro cúbico". La atmósfera de la Tierra al nivel del mar, en comparación, es mil millones de millones de millones (1021) de veces más densa. Y finalmente, la velocidad del flujo es de 26 km/seg o 58,000 millas por hora. Estos números confirman lo que los astrónomos han sospechado durante mucho tiempo. El Sistema Solar está colisionando con una enorme nube interestelar. Mucha gente cree que el espacio está vacío, pero no lo está. El "vacío" entre las estrellas está abarrotado de nubes de gas. La amplitud de las nubes en la Tierra se mide en millas. La de las nubes en el espacio se mide en años luz. Varían en su tipo desde las frías y negras como la tinta hasta un pintoresco y caliente resplandor. Las estrellas nacen en las nubes, y aún arrojan más nubes al espacio cuando mueren. Las nubes interestelares están por todas partes, de modo que no es tan sorprendente que el Sistema Solar esté viajando dentro de una. La pregunta es, ¿Qué clase de nube? Ésta nube, como muchos otros objetos en el Universo, consta principalmente de hidrógeno. Sabemos esto porque el hidrógeno absorbe un indicador de color de la luz de las estrellas cercanas. Los astrónomos utilizan el efecto de la absorción para trazar el contorno general de la nube: tiene una anchura de varios años luz y un borde irregular. El abundante hidrógeno de la nube no penetra fácilmente en la heliósfera porque los átomos de hidrógeno de la nube están ionizados por la radiación interestelar ultravioleta. Al igual que los rayos cósmicos, los átomos de hidrógeno tienen carga, por eso, se mantienen acorralados. Los átomos de helio, por otro lado, son principalmente neutros, de modo que se deslizan al interior del Sistema Solar. Aunque el helio es sólo un ingrediente menor de la nube, esto indica a los investigadores el aspecto de la totalidad. La temperatura de la nube es de 6000ºC, la misma que la del flujo de helio. Su velocidad, 26 km/seg, es también la misma. Si la nube contiene una mezcla cósmica estándar de hidrógeno y helio – una suposición razonable—entonces su densidad global debe ser de 0.264 átomos por centímetro cúbico. ¿Arcania? En absoluto. Estos números son importantes. Son vitales para el tamaño y "el resquebrajamiento" de la heliósfera. La burbuja se infla desde dentro a causa del viento solar y se comprime desde el exterior por la acción de la nube. Es un acto de equilibrio. Si la presión de la nube (en función de la temperatura, densidad y velocidad) es elevada, vence al viento solar y hace que la burbuja se reduzca, lo cual disminuye nuestras defensas contra los rayos cósmicos. Dentro de miles de años, algunos investigadores creen, que el Sistema Solar, atravesará completamente esta nube y emergerá en una cavidad de baja presión enviada por esas supernovas hace pocos millones de años. La heliósfera se expandirá, proporcionando una mejor protección contra los rayos cósmicos. Después... ¿quién sabe? Otra nube podría llegar y comprimir otra vez la burbuja. El equipo de investigación ISSI, finalmente, podría decirnos como reaccionará la heliósfera. http://www.laflecha.net/canales/ciencia/200410111/

Astronomía Detectan objeto "misterioso" con campo magnético superior al Sol La masa de este objeto estelar es "demasiado grande" para considerarlo un superplaneta pero, al ser más pequeña, tampoco puede identificarse con una estrella, por lo que resulta "imposible" encuadrarlo en ninguna categoría. (EFE) MADRID, octubre 07.- Un equipo de astrónomos ha descubierto un objeto "misterioso", situado en la constelación Eridanus, a 300 años luz de la Tierra, con un campo magnético 14 millones de veces superior al del Sol. Según un estudio que se publicará en el próximo número de la revista "Astrophysical Journal", el objeto estelar no identificado era inicialmente una estrella con un tamaño similar al del Sol, que podría haber ido perdiendo su masa al interactuar con otro astro cercano. Para uno de los miembros del equipo de astrónomos que realizó la investigación, Thomas E. Harrison, la masa de este objeto estelar es "demasiado grande" para considerarlo un superplaneta pero, al ser más pequeña, tampoco puede identificarse con una estrella, por lo que resulta "imposible" encuadrarlo en ninguna categoría. La investigación fue llevada a cabo en el archipiélago estadounidense de Hawai con los telescopios Gemini North y Keck II. Según Harrison, el objeto enano capaz de emitir todavía "grandes cantidades" de luz podría proceder de una estrella solar con un tamaño similar al del Sol, que habría perdido parte de su masa al interactuar con su estrella vecina, hasta llegar a convertirse en un objeto enano. Entre ambas estrellas se produjo un proceso de transferencia de masa con explosiones que, según Harrison, causaron el acercamiento de sus órbitas hasta el punto de que, en la actualidad, la distancia que las separa es similar a la existente entre la Tierra y la Luna. Las causas de que se iniciara el proceso de transferencia de masa constituyen una incógnita. http://www.terra.cl/noticias/noticias.cfm?id_reg=422855&id_cat=1167

16:38 | Astrronomía Detectan un objeto misterioso en la constelación de Eridanus Un equipo de astrónomos ha descubierto un objeto "misterioso", situado en la constelación Eridanus, a 300 años luz de la Tierra, con un campo magnético 14 millones de veces superior al del Sol, según un estudio que se publicará el próximo número de la revista Astrophysical Journal. De acuerdo a la investigación, el objeto estelar indeterminado se trataba al principio de una estrella con un tamaño similar al del Sol, que podría haber ido perdiendo su masa al interactuar con otra estrella próxima. La masa de este objeto estelar es "demasiado grande" para ser un superplaneta pero, al ser excesivamente pequeña, tampoco puede identificarse con una estrella, por lo que resulta "imposible" encuadrarlo en ninguna categoría, aseguró Thomas E. Harrison, uno de los miembros del equipo de astrónomos. La investigación, llevada a cabo en Hawai con los telescopios Gemini North y Keck II, ha revelado la existencia de un sistema de estrellas binario formado por una estrella con el 60 por ciento de masa solar y un objeto estelar enano con un volumen de "sólo" 1/20.000 de masa solar. Harrison estimó que el objeto enano capaz de emitir todavía "grandes cantidades" de luz podría proceder de una estrella solar que podría haber tenido un tamaño similar al del Sol. Esta estrella podría haber ido perdiendo parte de su masa al interactuar con su estrella vecina hasta llegar a convertirse en un objeto enano. A juicio de Harrison, entre ambas estrellas se produjo un proceso de transferencia de masa con explosiones que causaron el acercamiento de sus órbitas hasta el punto de que, en la actualidad, la distancia que las separa es similar a la existente entre la Tierra y la Luna. Sin embargo, las causas que causaron el inicio de este proceso de transferencia de masa constituyen una incógnita, subraya el estudio. http://www.diariohoy.net/v5/verNoticia.phtml/html/135717/

Altas energías en el centro de la galaxia SERVICIOS Enviar esta página Imprimir esta página Contactar Anterior Volver Siguiente Levante-EMV, Londres Un objeto que emite rayos gamma de alta energía ha sido detectado por un equipo internacional de astrónomos en el centro de nuestra galaxia, la Vía Láctea. Utilizaron para ello el High Energy Stereoscopic System (HESS), un nuevo grupo de cuatro radiotelescopios instalado en Namibia, en el África suroccidental. El centro galáctico aloja varias fuentes potenciales de rayos gamma, incluyendo un agujero negro supermasivo, restos de explosiones supernovas y posiblemente una acumulación de partículas exóticas de ÜÜmateria oscuraÝÝ, cada una de las cuales debería emitir la radiación de forma ligeramente distinta. La que ha sido observada con el HESS procede de una región muy próxima a Sagitario A*, el agujero negro que se halla en el centro de la galaxia. Según las más recientes teorías, la radiación es demasiado energética como para haber sido creada por la aniquilación de partículas de materia oscura. En cambio, el espectro de energía encaja bastante bien con la teoría de que la fuente podría ser una explosión supernova, que debería producir un chorro constante de radiación. Sabemos que hace 10.000 años estalló una supernova en dicha región, explica la Dr. Paula Chadwick, de la University of Durham. Tal explosión podría acelerar los rayos gamma cósmicos hasta los niveles de energía observados, mil millones de veces superiores a los de la radiación utilizada en los rayos-X de hospitales. A pesar de todo, serán necesarias más observaciones para confirmar la fuente exacta de las emisiones. Los resultados obtenidos, sin embargo, no coinciden con los producidos por otros instrumentos, como el americano Whipple o el japonés/australiano CANGAROO, los cuales midieron los rayos gamma procedentes del centro galáctico entre 1995 y 2002. Las características son distintas, por lo que los astrónomos piensan que podría tratarse de una fuente que varía a lo largo del año. Se trataría entonces de un objeto variable, apoyando la posibilidad de que el responsable sea el agujero negro central. Durante los dos próximos años, el equipo del HESS continuará realizando observaciones para discernir la solución al problema. No en vano el trabajo del complejo apenas acaba de empezar; el sistema completo de cuatro radiotelescopios se inauguró apenas el pasado 29 de septiembre de 2004. http://www.levante-emv.com/secciones/noticia.jsp?pIdNoticia=55113&pIndiceNoticia=1&pIdSeccion=23

UNIVERSO El entorno del centro de la Vía Láctea es letal para la vida La vida cerca del centro de nuestra galaxia no tiene prácticamente modo de surgir, pues cada 20 millones de años en promedio las masas de gas fluyen por el centro galáctico y colisionan, creando millones de nuevas estrellas. Las estrellas más masivas pronto se convierten en supernovas, explotando violentamente y irradiando en el espacio circundante grandes cantidades de energía que lo esterilizan por completo. Éste escenario se detalla en el número del 10 de octubre la revista The Astrophysical Journal Letters, por el equipo del astrónomo Antony Stark. 16:08 - 12/10/2004 | Fuente: ASTROENLAZADOR El descubrimiento del equipo fue posible gracias a las capacidades únicas del Telescopio Antártico Submilimétrico y Observatorio Remoto (ART/RO), el único del mundo capaz de realizar mapas para estudiar el cielo en longitudes de onda submilimétricas. El gas que genera cada brote de formación estelar procede de un anillo de material localizado a 500 años luz del centro de la galaxia. Dicho gas se agrupa bajo la influencia del núcleo galáctico, un conjunto compacto de estrellas de 6000 años luz de longitud que rota en la parte central de la Vía Láctea. Las fuerzas de marea y las interacciones con esta región de la Vía Láctea contribuyen a que el anillo de gas vaya alcanzando densidades cada vez mayores hasta llegar a un punto crítico, en el cual éste acaba precipitándose masivamente hacia el centro galáctico y acumulándose, produciendo una enorme brote de formación estelar. Los astrónomos observan brotes de formación estelar en muchas galaxias, frecuentemente cuando tienen lugar colisiones entre éstas, lo cual produce como consecuencia la acumulación de ingentes masas de gas. De todas formas, estos brotes también pueden producirse en galaxias aisladas, incluyendo la propia Vía Láctea. Según Stark, el próximo brote de formación estelar en la Vía Láctea tendrá lugar relativamente pronto, aproximadamente en los próximos 10 millones de años. Esta predicción se basa en las medidas realizadas por el equipo de científicos, que muestran que la densidad del gas en el anillo situado en torno al núcleo galáctico se acerca a la densidad crítica. Una vez se cruce esta barrera energética, el anillo colapsará comenzando así una intensa etapa de formación de nuevas estrellas: una masa equivalente a 30 millones de masas solares se desplazará hacia el interior de la galaxia, produciendo una saturación en el agujero negro -de 3 millones de masas solares- que se sitúa en el centro galáctico. A pesar de que el agujero negro es extremadamente masivo, éste será incapaz de consumir la mayor parte del gas, el cual constituirá el combustible para crear millones de estrellas nuevas. Las estrellas más masivas consumen su combustible mucho más rápidamente que aquellas más livianas, agotándolo en sólo unos pocos millones de años y dando como resultado la explosión de supernovas, que irradian energía al espacio circundante. Debido a que estas regiones de la Vía Láctea presentan una alta densidad estelar, toda la región del centro galáctico sufrirá una irradiación tan dramática que será capaz de aniquilar cualquier tipo de vida que se hubiese formado en un planeta de tipo terrestre. Afortunadamente, la Tierra se encuentra a unos de 25.000 años luz del centro galáctico, lo suficientemente lejos para no hallarse en peligro. Las instalaciones empleadas para realizar este descubrimiento, AST/RO, consisten en un telescopio de 1.7 metros de diámetro que opera en uno de los ambientes más extremos de planeta, los desiertos de la Antártida. Este instrumental se encuentra localizado en la estación Amundsen-Scott localizada en el polo sur y a cargo de la National Science Foundation. El aire en el el polo sur es muy seco y frío, por lo cual la radiación que en otros sitios es absorbida por el vapor de agua puede ser detectada en esta región a nivel de superficie http://www.laflecha.net/canales/ciencia/200410115/

12/Oct/04 Explosiones estelares frecuentes esterilizan el centro de la Vía Láctea La vida en las vecindades del centro de nuestra galaxia nunca debe haber tenido una oportunidad. Cada 20 millones de años en promedio, el gas se abre camino hacia el centro galáctico y allí explota, creando millones de nuevas estrellas. Las más masivas terminan en poco tiempo convirtiéndose en supernovas, que luego al explotar violentamente arrasan el espacio circundante con la suficiente energía como para esterilizarlo completamente. Este escenario está detallado por el astrónomo Anthony Stark y sus colegas del Centro Harvard-Smithsoniano para Astrofísica, en el articulo aparecido en la entrega del 10 de Octubre del Astrophysical Journal Letters. El equipo de investigadores pudo realizar este descubrimiento gracias a las características únicas del Telescopio Antártico Submilimétrico y Observatorio Remoto (AST/RO). Es el único observatorio en el mundo capaz de realizar mapas en gran escala del cielo en las longitudes de onda submilimétricas. El gas de cada explosión proviene de un anillo de material ubicado a aproximadamente 500 años-luz de distancia del centro de la galaxia. El gas se aglomera allí bajo la influencia de la Barra Galáctica, un óvalo estirado de estrellas de unos 6000 años-luz de largo que está rotando en el medio de la Vía Láctea. Las fuerzas de marea e interacciones con esta Barra provocan que el anillo de gas se comprima a densidades cada vez más altas hasta que llega a una densidad crítica o punto de vuelque. En ese punto el gas se precipita hacia el centro galáctico aplastándose sobre sí mismo, lo que inicia una enorme actividad de formación de estrellas. "Una erupción estelar es cuando la formación de estrellas se vuelve frenética", dice Stark. Los astrónomos ven erupciones en muchas galaxias, aunque mayormente sucede que éstas están colisionando con otras galaxias, hecho que provoca que enormes cantidades de gas interaccionen entre sí. Pero también las erupciones pueden ocurrir en galaxias aisladas, incluyendo la nuestra: la Vía Láctea. "La próxima erupción en nuestra Vía Láctea es dentro de relativamente poco tiempo", predice Stark. "Es posible que suceda dentro de los próximos 10 millones de años". Esta aseveración se basa en las medidas, tomadas por el equipo de astrónomos, que muestran que la densidad de gas en el anillo está muy cercana a su valor crítico. Una vez que se cruce ese umbral, el anillo colapsará y provocará una erupción que resplandecerá a una escala de proporciones inimaginables. Cerca de 30 millones de masas solares de materia fluirán hacia adentro, arrasando el agujero negro de 3 millones de masas solares que se encuentra en el centro galáctico. El agujero negro, a pesar de su enorme masa, no será capaz de consumir la mayoría del gas. "Va a ser como si intentáramos llenar un cubo de agua para el perro usando una manguera de bomberos", dice Stark. Así que, en lugar de consumirse, la mayoría del gas formará millones de nuevas estrellas. Y cuanto más masivas sean las estrellas formadas, más rápidamente quemarán su combustible, agotándolo en unos pocos millones de años. Luego, explotarán como supernovas lo que irradiará su espacio circundante. Con tantas estrellas apiñadas tan cercanas unas a las otras como resultado de la erupción, todo el centro galáctico será impactado de forma lo suficientemente dramática como para aniquilar toda la vida en un planeta como la Tierra. Afortunadamente, la Tierra misma está a unos 25.000 años-luz de distancia, lo suficientemente lejos como para no estar en peligro. El dispositivo que fue utilizado para realizar este descubrimiento, el AST/RO, es un telescopio de 1,7 metros de diámetro que opera en uno de los entornos mas desafiantes del planeta: en el glacial desierto de la Antártida. Está emplazado en la estación Amundsen-Scott, de la National Science Fundation (NSF), ubicada en el Polo Sur. El aire en el polo sur es extremadamente seco y frío, lo que permite que, a diferencia que en otros lugares, la radiación que de otra forma sería absorbida por el vapor de agua pueda llegar hasta la superficie y allí ser detectada. "Estas observaciones han ayudado a avanzar en nuestro entendimiento sobre la formación de estrellas en la Vía Láctea", dice Stark. "Esperamos continuar con estos avances con colaboraciones con investigadores que están trabajando en el Programa Patrimonio Científico del Telescopio Espacial Spitzer. Las observaciones realizadas en el AST/RO son complementarias y podrán contribuir de manera excepcional con tal esfuerzo". Junto con Stark, los coautores del articulo que anuncian estos descubrimientos son: Christopher L. Martin, Wilfred M. Walsh, Kecheng Xiao y Adair P. Lane, todos del Centro Harvard-Smithsoniano para Astrofísica, y además: Christopher K. Walker, del observatorio Steward. Localizado en Cambridge, estado de Massachussets, el Centro Harvard-Smithsoniano para Astrofísica (CfA) es una colaboración entre el Observatorio de Astrofísica Smithsoniano y el Observatorio de la Universidad de Harvard. Los investigadores del CfA, organizados en seis divisiones de investigación, estudian el origen, la evolución y el destino final del universo. Traducido por Leando Conde, equipo Axxón Más datos: Astrobiology http://axxon.com.ar/not/143/c-1430098.htm

Fuente de energía en Vía Láctea En el universo las fuentes de energía se multiplican. WINDHOEKE, NAMIBIA (Agencias).- Un objeto que emite rayos gamma de alta energía ha sido detectado por un equipo internacional de astrónomos en el centro de la Vía Láctea. Para ello utilizaron el High Energy Stereoscopic System (HESS), un novísimo grupo de cuatro radiotelescopios instalado en Namibia, en el África suroccidental. El centro galáctico aloja varias fuentes potenciales de rayos gamma, incluyendo un agujero negro supermasivo, restos de explosiones supernovas y posiblemente una acumulación de partículas exóticas de “materia oscura”, cada una de las cuales debería emitir la radiación de forma ligeramente distinta. La que ha sido observada con el HESS procede de una región muy próxima a Sagitario A, el agujero negro que se halla en el centro de la galaxia. TEORÍAS Según las más recientes teorías, la radiación es demasiado energética como para haber sido creada por la aniquilación de partículas de materia oscura. En cambio, el espectro de energía encaja bastante bien con la teoría de que la fuente podría ser una explosión supernova, que debería producir un chorro constante de radiación. Se sabe que hace diez mil años estalló una supernova en dicha región. Tal explosión podría acelerar los rayos gamma cósmicos hasta los niveles de energía observados, mil millones de veces superiores a los de la radiación utilizada en los rayos-X de los hospitales. FUENTE VARIABLE Pero los resultados obtenidos no coinciden con los producidos por otros instrumentos, como el americano Whipple o el japonés/australiano CANGAROO, que midieron los rayos gamma procedentes del centro galáctico entre 1995 y 2002. Las características son distintas, por lo que los astrónomos piensan que podría tratarse de una fuente que varía a lo largo del año. Se trataría entonces de un objeto variable, apoyando la posibilidad de que el responsable sea el agujero negro central. Durante los dos próximos años, el equipo del HESS continuará realizando observaciones para discernir la solución al problema. http://www.elsiglodedurango.com.mx/kiosko/nID/31246/

Por Pascal Barollier AFP Washington, U.S., 18 de mayo, 2004 (AFP) - El Universo se expande a un ritmo cada vez más rápido, anunciaron este martes investigadores británicos, confirmando por observación directa teorías de implicaciones fundamentales para el futuro del cosmos. Estas conclusiones se fundan en la observación de "la energía oscura" (dark energy) con la ayuda del telescopio espacial de rayos-X Chandra, señalaron los autores reunidos en Washington para una conferencia de prensa en la sede de la NASA. "El Universo se acelera verdaderamente, es una confirmación directa que tiene importantes implicaciones para el futuro de nuestro Universo", estimó Steve Allen, astrofísico del Instituto de Astronomía de Cambrigde (Gran Bretaña), que dirigió los trabajos. "La energía oscura empuja (al Universo) hacia el exterior y acelera su expansión", agregó. Los investigadores ignoran la composición de esta energía, pero estiman que su densidad determina el ritmo de la expansión del Universo. "La expansión del universo se acelera y actualmente la cuestión es saber porqué", comentó Paul Hertz, investigador de la NASA. "Hasta que no comprendamos qué compone la energía oscura, todas las opciones son posibles" para el futuro del Universo, añadió. Tres escenarios existen en función de la densidad de la energía oscura. Si su densidad permanece constante, la aceleración de la expansión va a continuar y "sólo en miles de millones de años, el cielo en lugar de tener las miles de millones de galaxias observables con el telescopio, comprenderá tan solo unas cientas; será un lugar muy solitario", estimó Hertz. En cambio, si la densidad se reduce, "la expansión va a decrecer hasta el punto donde el Universo se va a desplomar nuevamente antes de un derrumbe" general y una desaparición del Universo, antes de que quizá ocurra un nuevo Big Bang. La tercera opción sería un aumento de la densidad de la energía oscura, cuyo efecto último sería "una destrucción de los átomos que componen toda la materia", agregó. "La energía oscura domina el Universo y podría dominarlo aún más" en el futuro, indicó el profesor Allen, para quien la teoría formulada por Albert "Einstein de una densidad constante de la energía oscura parece ser un buen modelo" de trabajo para los investigadores. Pero en "tanto no tengamos una mejor comprensión de la aceleración cósmica y de la naturaleza de la energía oscura, no podremos comprender el destino del Universo", resaltó Michel Turner, investigador independiente de la Universidad de Chicago y de la Fundación Nacional de Ciencias de Estados Unidos. Los investigadores que realizaron el estudio estiman que el universo está compuesto de un 75% de energía oscura, un 21% de materia oscura y sólo un 4% de materia normal como la que compone la Tierra. Para su trabajo, los científicos estudiaron 26 grupos de galaxias a distancias situadas a 8.000 millones de años luz. AFP http://www.quepasa.com/content/?c=208&id=257929

Jueves, 04 de Noviembre de 2004 Actualizado a las 05:01 (CET) - Internet time @209 by CIENTÍFICOS INTERNACIONALES REALIZAN LA PRUEBA Consiguen la primera imagen de un objeto astronómico gracias a la energía de los rayos gamma EUROPA PRESS NOTICIAS RELACIONADAS MADRID.- Un equipo internacional de astrónomos ha conseguido la primera imagen nunca realizada de un objeto astronómico usando la potente energía de los rayos gamma, lo que puede ayudar a resolver el origen de los rayos cósmicos. Su investigación, publicada esta semana en la revista 'Nature', se realizó usando el Sistema de Alta Energía Estereoscópica, de cuatro telescopios, situado en Namibia (Sudáfrica). Los astrónomos estudiaron los restos de una supernova que explotó hace 1.000 años, dejando tras de sí una estela de desechos, que vistos desde la Tierra, suponen dos veces el diámetro de la Luna. La imagen resultante ayuda a resolver el misterio que los científicos persiguen desde hace 100 años: el origen de los rayos cósmicos, que son partículas extremadamente energéticas que bombardean la Tierra continuamente. De hecho, miles de ellas pasan a través de nuestros cuerpos cada día. La producción de rayos gamma en esta oleada de partículas chocantes procedentes de la supernova indica que ésta actúa como un acelerador gigante de partículas, y de esa manera se convierte en una fuente probable de rayos cósmicos en nuestra galaxia. Según Ian Halliday, uno de los principales colaboradores del estudio, "los resultados suministran la primera prueba inequívoca de que las supernovas son capaces de producir grandes cantidades de rayos cósmicos galácticos, algo que se sospechaba desde hace bastante tiempo, pero que nunca se había podido confirmar". La radiación más penetrante que se conoce procede de los rayos gamma, ya que son alrededor de un billón de veces más energéticos que los rayos que pudiera producir una máquina de rayos X de un hospital. Esto hace muy difícil usarlos para crear una imagen, ya que pasan directamente a través de cualquier superficie que pudiera utilizarse para reflejarlos. Los rayos gamma de los objetos en el espacio exterior no llegan hasta la Tierra ya que son detenidos por la atmósfera, de forma que cuando esto ocurre se produce un pálido destello de luz azul que dura algunas billonésimas partes de segundo. Los astrónomos utilizaron imágenes de estos destellos de luz, llamada radiación Cherenkov, para hacer una 'imagen' con rayos gamma por primera vez. http://www.elmundo.es/elmundo/2004/11/04/ciencia/1099527507.html

Identifican el desencadenante de la supernova de Tycho Brahe Astronomía -------------------------------------------------------------------------------- En noviembre de 1572, el astrónomoTycho Brahe descubrió una estrella en la constelación de Casiopea, tan brillante como Júpiter, y publicó sus observaciones en el libro “De Nova Stella”. Era una supernova del tipo Ia, y brilló intensamente en el cielo hasta marzo de 1574. La estrella descrita por Tycho Brahe y otros astrónomos del siglo XVI era una explosión cósmica de estrellas binarias. Pero hasta hoy día no se había identificado el componente superviviente del sistema binario (es decir, el que desencadenó la explosión de la otra estrella). Ésta es una primicia que anuncia hoy el 28 de octubre la revista Nature, en una investigación liderada por la profesora Pilar Ruiz-Lapuente del Departamento de Astronomía y Meteorología de la UB. La estrella candidata, a más de 10.000 años-luz de la Tierra, se desplaza a una velocidad tres veces superior a la de extrellas próximas, és más antigua que el Sol y está en fase de expansión, evolucionando hacia una gigante roja. En la época de Tycho Brahe, la inmutabilidad del cielo y la imposibilidad de aparición de nuevas estrellas en la bóveda celeste eran ideas comunes. El brillo de la nueva estrella abrió fisuras en la visión aristotélica del Universo, vigente desde la Antiguedad. La investigación para encontrar el compañero estelar de la supernova se inició en la UB en 1997, con el apoyo de telescopios del European Northern Observatory. Para identificar la estrella superviviente de la explosión, el equipo reconstruyó el escenario del cataclismo cósmico, pero 432 años más tarde. En el punto en donde Tycho Brahe vió la brillante estrella, en la actualidad hay una nebulosa de gas, resultado de la violenta explosión cósmica. Es el Remanente de la Supernova de Tycho. Para eliminar sistemas estelares como posibles progenitores de la supernova, los expertos han hecho estudios estos últimos años con diversos telescopios (Hubble Space Telescope, William Herschel Telescope y W.M. Keck Telescope). Descubrir la estrella compañera ha sido clave para defender la hipótesis más aceptada hoy día sobre las supernovas tipo Ia: un sistema binario de estrellas, con una enana blanca en órbita alrededor de otra estrella menos densa que le transfiere materia. Cuando se llega al límite de Chandrasekhar, la estrella estalla en una explosión similar a la de una bomba de fusión nuclear. Los resultados de la investigación abren vías de conexión entre explosiones de supernovas tipo Ia y las variables cataclísmicas. Las supernovas son la fase final de la evolución estelar: explotan y su brillo puede durar meses e incluso años. La radiación emitida en la explosión es utilizada por los astrónomos para el cálculo de distancias astronómicas. Son puntos de referencia para encontrar respuestas fundamentales sobre el origen y la evolución del Universo y para medir parámetros cosmológicos (expansión acelerada, materia oscura, etc.). Las de tipo Ia son explosiones titánicas, tan brillantes como las galaxias en donde se producen, visibles a billones de años-luz. De hecho, el descubrimineto de la aceleración de la expansión cósmica ha devuelto el protagonismo la constante cosmológica, una componente del Universo con presión negativa propuesta por Albert Einstein en 1917. A pesar de su importancia, es ahora cuando se empieza a conocer cómo se producen este tipo de supernovas. Más información: Dra. Pilar Ruiz-Lapuente Dept. Astronomia y Meteorología Tf: 93 402 11 20 mailto: [email protected] http://100cia.com/noticias/index.php?subaction=showfull&id=1098951912&archive=&start_from=&ucat=6

Jueves, 04 de Noviembre de 2004 Actualizado a las 05:01 (CET) - Internet time @209 by CIENTÍFICOS INTERNACIONALES REALIZAN LA PRUEBA Consiguen la primera imagen de un objeto astronómico gracias a la energía de los rayos gamma EUROPA PRESS NOTICIAS RELACIONADAS MADRID.- Un equipo internacional de astrónomos ha conseguido la primera imagen nunca realizada de un objeto astronómico usando la potente energía de los rayos gamma, lo que puede ayudar a resolver el origen de los rayos cósmicos. Su investigación, publicada esta semana en la revista 'Nature', se realizó usando el Sistema de Alta Energía Estereoscópica, de cuatro telescopios, situado en Namibia (Sudáfrica). Los astrónomos estudiaron los restos de una supernova que explotó hace 1.000 años, dejando tras de sí una estela de desechos, que vistos desde la Tierra, suponen dos veces el diámetro de la Luna. La imagen resultante ayuda a resolver el misterio que los científicos persiguen desde hace 100 años: el origen de los rayos cósmicos, que son partículas extremadamente energéticas que bombardean la Tierra continuamente. De hecho, miles de ellas pasan a través de nuestros cuerpos cada día. La producción de rayos gamma en esta oleada de partículas chocantes procedentes de la supernova indica que ésta actúa como un acelerador gigante de partículas, y de esa manera se convierte en una fuente probable de rayos cósmicos en nuestra galaxia. Según Ian Halliday, uno de los principales colaboradores del estudio, "los resultados suministran la primera prueba inequívoca de que las supernovas son capaces de producir grandes cantidades de rayos cósmicos galácticos, algo que se sospechaba desde hace bastante tiempo, pero que nunca se había podido confirmar". La radiación más penetrante que se conoce procede de los rayos gamma, ya que son alrededor de un billón de veces más energéticos que los rayos que pudiera producir una máquina de rayos X de un hospital. Esto hace muy difícil usarlos para crear una imagen, ya que pasan directamente a través de cualquier superficie que pudiera utilizarse para reflejarlos. Los rayos gamma de los objetos en el espacio exterior no llegan hasta la Tierra ya que son detenidos por la atmósfera, de forma que cuando esto ocurre se produce un pálido destello de luz azul que dura algunas billonésimas partes de segundo. Los astrónomos utilizaron imágenes de estos destellos de luz, llamada radiación Cherenkov, para hacer una 'imagen' con rayos gamma por primera vez. http://www.elmundo.es/elmundo/2004/11/04/ciencia/1099527507.html

Ciencia ¡Activar escudos! 06/11/2004 La nube local interestelar Si alguna vez usted ha visto Star Trek, entonces sabe la importancia que tienen los escudos. Cuando una estrella explota o un Klingon lanza sus mortíferos rayos en la oscuridad, el capitán grita dos palabras "¡Activar escudos!", y todo va bien. Escudos deflectores: no salgas de casa sin uno. El Sistema Solar, créalo o no, tiene uno. El escudo deflector del Sistema Solar es una grande burbuja magnética llamada "heliosfera". Es parte del campo magnético del Sol. Nadie sabe las dimensiones exactas de la heliosfera, pero es más grande que la órbita de Plutón. Los nueve planetas están dentro de ella. La heliosfera es importante para la vida en nuestro planeta. Hace unos pocos millones de años, por ejemplo, un grupo de estrellas masivas fluctuaban a través de nuestra parte de la Vía Láctea y explotaron una después de la otra, como palomitas de maíz. Los rayos cósmicos de la explosión fueron en su mayor parte desviados, evitando un baño de radiación sobre los primeros humanos. Pero la burbuja no es perfecta. El hecho es que "está horadada - tiene escapes" dice el científico espacial Eberhard Moebius de la Universidad de New Hampshire. "Algunas cosas se filtran a través de ella". (Esto también sucede en Star Trek. Si los escudos de la nave fueran impenetrables, faltaría la emoción dramática). Tomemos los rayos cósmicos como ejemplo. Son fragmentos de átomos rotos en pedazos y acelerados a la velocidad de la luz por las explosiones de supernovas. La heliosfera desvía cerca de un 90% de éstos; el resto, el 10% de los más poderosos, penetra en el interior del Sistema Solar. La burbuja es incluso más vulnerable para partículas sin carga eléctrica. Los campos magnéticos pueden desviar partículas cargadas como los rayos cósmicos, pero no los átomos y moléculas neutras o trozos de polvo y roca. Para éstos, la burbuja es una puerta abierta. Veamos: un flujo de átomos neutros de helio -"una brisa interestelar", dice Moebius- fluye ahora mismo hacia el interior del Sistema Solar. "Su dirección proviene de la constelación de Sagitario. Como los átomos del flujo no están cargados, la burbuja magnética no puede hacer nada para detenerlos". Estudiar este flujo es importante porque puede enseñarnos mucho sobre la heliosfera: ¿Qué tan grande es?, ¿Cuán horadada está? También puede enseñarnos sobre la "materia" interestelar escondida ahí fuera", dice Moebius. El flujo, descubierto hace 30 años, es monitoreado activamente por una flotilla de naves de la Nasa y de la Agencia Espacial Europea: Soho, Euve, ACE y, especialmente Ulises. Cada una mide algo diferente. Euve, por ejemplo, puede percibir la luz ultravioleta del Sol dispersa en el flujo, mientras la Ulises toma muestras del propio flujo, recogiendo átomos directamente de éste. Durante muchos años las características físicas del flujo sólo eran vagamente conocidas. "Pero la capacidad que tenemos ahora para observar la corriente con detalle usando estas modernas naves es lo que marca la diferencia" dice Moebius. Recientemente dirigió un equipo de investigación en el Instituto Internacional de Ciencias del Espacio (International Space Science Institute, Issi) en Suiza; empleando datos de estas naves, pudieron precisar la temperatura del flujo, densidad y velocidad: Su temperatura, 6000 ºC, es más o menos la misma que la existente en la superficie del Sol. Una nave espacial volando a través del flujo no se fundirá, ni siquiera notará el calor. El gas en el flujo es tenue y fino, explica Moebius. "Sólo hay 0.015 átomos de helio por centímetro cúbico". La atmósfera de la Tierra al nivel del mar, en comparación, es mil millones de billones (1021) de veces más densa. Y finalmente, la velocidad del flujo es de 26 km/seg o 58,000 millas por hora. Un vacío que no lo es tanto Estos números confirman lo que los astrónomos han sospechado durante mucho tiempo. El Sistema Solar está colisionando con una enorme nube interestelar. Mucha gente cree que el espacio está vacío, pero no lo está. El "vacío" entre las estrellas está abarrotado de nubes de gas. La amplitud de las nubes en la Tierra se mide en kilómetros. La de las nubes en el espacio se mide en años luz. Varían en su tipo desde las frías y negras como la tinta hasta un pintoresco y caliente resplandor. Las estrellas nacen en las nubes, y aún arrojan más nubes al espacio cuando mueren. Las nubes interestelares están por todas partes, de modo que no es tan sorprendente que el Sistema Solar esté viajando dentro de una de ellas. La pregunta es: ¿Qué clase de nube? Esta nube, como muchos otros objetos en el Universo, está formada principalmente de hidrógeno. Sabemos esto porque el hidrógeno absorbe un indicador de colores de la luz cercana a las estrellas. Los astrónomos utilizan el efecto de la absorción para trazar el contorno general de la nube: tiene una anchura de varios años luz y un borde irregular. El abundante hidrógeno de la nube no penetra fácilmente en la heliosfera porque los átomos de hidrógeno de la nube están ionizados por la radiación interestelar ultravioleta. Al igual que los rayos cósmicos, los átomos de hidrógeno tienen carga eléctrica, por eso, se mantienen acorralados. Los átomos de helio, por otro lado, son principalmente neutros, de modo que se deslizan al interior del Sistema Solar. Aunque el helio es sólo un ingrediente menor de la nube, sirve para indicar a los investigadores su composición total. La temperatura de la nube es de 6000ºC, la misma que la del flujo de helio. Su velocidad, 26 km/seg, es también la misma. Si la nube contiene una mezcla cósmica estándar de hidrógeno y helio -una suposición razonable- entonces su densidad global debe ser de 0.264 átomos por centímetro cúbico. ¿Detalles triviales? En absoluto. Estos números son importantes. Son vitales para el tamaño y "la porosidad" de la heliosfera. La burbuja se infla desde dentro a causa del viento solar y se comprime desde el exterior por la acción de la nube. Es un acto de equilibrio. Si la presión de la nube (en función de la temperatura, densidad y velocidad) es elevada, vence al viento solar y hace que la burbuja se reduzca, lo cual disminuye nuestras defensas contra los rayos cósmicos. Dentro de miles de años, creen algunos investigadores, el Sistema Solar atravesará completamente esta nube y emergerá en una cavidad de baja presión originada por esas supernovas hace pocos millones de años. La heliosfera se expandirá, proporcionando una mejor protección contra los rayos cósmicos. Después... ¿quién sabe? Otra nube podría llegar y comprimir nuevamente la burbuja. Las investigaciones del equipo Issi, eventualmente, podrían decirnos como reaccionará la heliosfera. ¿Activar escudos? ¿Desactivar escudos? Ya no es ciencia ficción. http://www.correodelcaroni.com/seccion.asp?pid=43&sid=1237¬id=114199

ASTRONOMÍA Los astrónomos tendrán que revisar sus teorías tras los planetas extrasolares hallados Los gigantescos planetas extrasolares descubiertos hasta la fecha han sorprendido a los astrónomos y obligarán a revisar las teorías en este campo, pues, al contrario de lo que se pensaba, están próximos a su estrella y tienen órbitas muy excéntricas, que son más propias de los cometas. 16:08 - 01/12/2004 | Fuente: AGENCIA EFE Así lo indicó el astrofísico Álvaro Giménez, que dirige el Departamento de Investigación y Apoyo Científico de la Agencia Europea del Espacio en Holanda, y que impartió una conferencia sobre este asunto dentro de los actos organizados con motivo de la XVI Escuela de Invierno del Instituto de Astrofísica de Canarias (IAC). Giménez subrayó que desde que en 1995 comenzaron a detectarse planetas extrasolares las teorías existentes sobre este asunto «no funcionan», ya que «lo lógico» sería que estos cuerpos tuviesen órbitas circulares y no estuviesen tan cercanos a su estrella, pues son gigantes y tienen una estructura gaseosa. «Algo está pasando para que no veamos sistemas planetarios» que funcionan como el Solar, cuyos planetas tienen una órbita estable, mientras que en el caso de los extrasolares descubiertos en vez de tardar once años en orbitar alrededor de la estrella, como sucede con Júpiter, lo hacen en una semana «y esto no lo entendemos». Los astrónomos sospechan que estos planetas gigantes se formaron «muy lejos» y por alguna razón «migraron» y movieron su órbita, lo que les fue acercando a la estrella y algunos «cayeron» sobre ella, y al trasladarse «ganaron excentricidad, por lo que tienen una órbita más parecida a un cometa que a la de un planeta». «Lo que se ha descubierto hasta ahora nos ha sorprendido porque los planetas no son nada parecidos a lo que esperábamos encontrar y son todos raros, gigantes, con mucha masa y órbita excéntrica», insistió el científico. Esclarecer el origen Desde un punto de vista físico es muy importante el estudio de los planetas gigantes, añadió Giménez, que ha trabajado en el Instituto Nacional de Técnica Aeroespacial y en el Consejo Superior de Investigaciones Científicas, ya que ayudarán a esclarecer el origen de los sistemas planetarios. Explicó que los planetas gigantes «dominan» en los procesos de formación al ser los más masivos, y detalló que la mayor cantidad de su masa se sitúa en el disco primigenio protoplanetario, al tiempo que mantienen el gas. Por el contrario, en los planetas similares a la Tierra la masa original está situada en su núcleo y han perdido el gas, que elimina el viento solar. No obstante, los astrónomos perfeccionan los métodos de detección de estos planetas extrasolares con el objetivo de localizar cuerpos parecidos a la Tierra y determinar si son más calientes, tienen atmósfera, cómo es su órbita y si presentan condiciones para ser «habitables», lo que sería factible con una temperatura que oscilase entre los 0 y los 100 grados centígrados. Pero para ello es necesario recurrir a proyectos espaciales, como el «Kepler» de la NASA o el «Corot» de la Agencia Europea del Espacio, o conseguir en los instrumentos terrestres una resolución 40 veces mayor que la del telescopio espacial, pues de lo contrario no se podrían detectar planetas parecidos a la Tierra. Los métodos actuales de detección, el de medir la velocidad radial del planeta, y el de tránsitos, son eficaces para localizar planetas gigantes, pues el menos masivo que se ha hallado tiene una masa parecida a Urano, que tiene 14 veces la de la Tierra. El siguiente paso en la detección de planetas extrasolares es el de analizar su luz y estudiar la composición de la atmósfera para buscar indicios de agua, dióxido de carbono, metano y otros componentes que indiquen la existencia de vida, que es el objetivo final, recordó el astrónomo. Observatorio en Chile La Agencia Europea del Espacio proyecta con este fin establecer en el Observatorio Austral de Chile un telescopio de cien metros de diámetro, que podría utilizar la técnica de la interferometría y tendría una resolución óptica suficiente para captar planetas de magnitud parecida a la terrestre. http://www.laflecha.net/canales/ciencia/200411299/