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By Daniel Fischer Every page present in Europe & the U.S.!
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The latest issue!
| A German companion! (SuW version) Current mission news: MGS (latest pictures!) + Cassini + Galileo + NEAR |
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Earth survives 'planet alignment'Next: very close conjunction of Venus & Jupiter on May 17Nothing happened, of course, when the 7 classical planets - Mercury to Saturn, the Moon and the Sun - had gathered in a 26 degree arc of the ecliptic on May 5th, a 'massing' visible directly only to the coronagraphic eye of the SOHO spacecraft. The "event", anticipated by esoteric minds for decades, is actually not even rare: On the long run, computer simulations of the Solar System have shown, the 5 naked-eye planets gather in an arc smaller than 25 degrees every 57 years. In 1962, e.g. they spanned an arc of only 16 degrees, also with the Moon, the Sun and even a total eclipse of the latter thrown in.The next massing, on Sept. 8, 2040, will be even more impressive, with the planets spanning only 10 degrees in the sky, this time in the evening sky, well away from the Sun. The same cannot be said, unfortunately, about an extremely close conjunction of Venus and Jupiter on May 17, 2000: While the planets will move so close together that their limbs are separated by only 22 seconds of arc, the show takes place only 7 degrees away from the Sun. Again an even more impressive event is in store in the future: In the year 2065 Venus will actually occult Jupiter partially, as seen from the Earth. |
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As many bodies beyond the Kuiper Belt as insideDuring the 1990s our knowledge about the Solar System beyond the orbit of Neptun has increased dramatically: Dozens of minor planets are now known to reside there in the so-called Kuiper belt (to which Pluto belongs, too). But in 1996 and 1999 four objects have been discovered that spend most of their orbit even beyond the main Kuiper Belt - and an admittedly vague extrapolation has now shown that both the number of bodies in this Scattered Kuiper Belt as well as their total mass could be similar to the main Kuiper Belt. There are thus three distinct classes of objects in this region:
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Hubble tracks down 'missing' baryonic matter in intergalactic spaceAccording to the cosmological view supported best by observations (see e.g. last Update story 3), at least 90 percent of the matter in the universe is hidden in exotic "dark" form that has not yet been seen directly. But more embarrassing is that, until now, most of the universe's ordinary, or baryonic, matter (mainly protons and neutrons), hadn't been seen either - the vast quantities of hydrogen that were cooked-up in the Big Bang had somehow managed to disappear into the empty blackness of space. Now Hubble spectroscopy of a distant quasar has turned up a 'tracer' for that missing gas, ionized oxygen: The hydrogen accounts for nearly half of the "normal" matter in the universe, with the rest locked up in myriad galaxies.The key observations were made with Hubble's Space Telescope Imaging Spectrograph (STIS) at the z=0.3 quasar QSO H1821+643: 4 definite absorption line systems of 5-times ionized oxygen (O VI) and one probable O VI absorber were seen in the spectrum between redshifts of 0.15 and 0.27. The four definite O VI absorbers are located near galaxies and are highly displaced from the quasar in redshift: These are likely intervening systems unrelated to the background QSO, probably part of a vast intergalactic network of chain-like structures of hydrogen gas that models of structure formation in the Universe predict. It is laced with oxygen and other heavier elements which were cooked up in stars in galaxies but blown out of those and shock-heated when meeting the intergalactic filaments. From the O VI absorption seen in the quasar spectrum one can calculate a cosmological mass density of the O VI systems Omega_b(O VI) > 0.0008 (for a Hubble constant of 75) - and with an assumed metallicity of 1/10 solar and a conservative assumption that the fraction of oxygen in the O VI ionization stage is 0.2, Omega_b(O VI) comes out greater than 0.004. This is comparable to the combined cosmological mass density of stars and cool gas in galaxies and X-ray emitting gas in galaxy clusters at low redshift. The confirmation of this missing hydrogen will shed new light on the large-scale structure of the universe. The detection also confirms fundamental models of how much hydrogen was manufactured in the first few minutes of the universe's birth in the Big Bang. (Tripp & al., Ap. J. Lett. 534 [May 1, 2000] L1-5) |
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Io's volcanoes splatter dust in the solar systemFiery volcanoes on Jupiter's moon Io are the main source of dust streams that flow from the Jupiter system into the rest of the solar system, according to new findings from NASA's Galileo spacecraft: There are peaks in the frequency of dust impacts on Galileo's dust detector subsystem that coincide with the periods of Io's orbit (approximately 42 hours) and of Jupiter's rotation (approximately 10 hours). Although dust scientists had long suspected Io as the source of the dust streams, it was difficult to prove, but several years of Galileo data show that the motion of the dust stream particles is strongly influenced by Jupiter's magnetic field, with a unique signature that could exist only if Io were the main contributor to the dust streams.The Jovian dust streams are intense bursts of submicron-sized particles (as small as particles of smoke) that originate in Jupiter's system and flow out about 290 million kilometers; they were first discovered in 1992 by the dust detector onboard the Ulysses spacecraft during its Jupiter flyby. These new results provide a useful window on Io: In-situ dust measurements can monitor the moon's volcanic plume activity, complementing observations made by other Galileo instruments as well as from Hubble or Earth-based telescopes. In December 2000, during a joint observation of Jupiter by Galileo and Cassini, scientists will have a unique opportunity to study the Jovian dust streams using dust instruments on both spacecraft. |
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Major NSF grant for the International Dark-Sky OrganizationAt its annual meeting on April 27, the International Dark-Sky Association (IDA) could announce a major grant from the National Science Foundation - it totals $150 000 and will be used to promote the organizational development of the IDA. Now supported by the NSF, the IDA seeks to preserve dark skies for the benefit of both professional and amateur astronomers, as well as the general public, by promoting outdoor lighting that focuses light only where it's needed - toward the ground. "The improper use of outdoor lighting is a serious problem for astronomers, the economy, as well as the general public," said Tom Gergely, NSF's director of electromagnetic spectrum management programs: "If we want to continue our exploration of the skies, we need systematic efforts to address light pollution. At the same time, communities and businesses can benefit from substantial energy savings, and the public may regain access to the beauty of the night sky."IDA's work is performed almost entirely by volunteers. The grant from NSF will help the organization expand its membership, develop a firm financial basis, and further develop public awareness of practical solutions to light pollution. Founded in 1988 as a nonprofit educational organization, the International Dark-Sky Association promotes quality outdoor lighting to control glare, to conserve energy, and to preserve the beauty of our night skies. IDA also works to protect radio astronomers from ever increasing radio frequency interference. In the past ten years, IDA has gained members from all 50 U.S. states and 70 countries, and it is growing rapidly. IDA's members include lighting designers, government planners and zoning officials, environmentalists, lighting manufacturers, astronomers, and other concerned citizens: This broad based membership yields very strong bipartisan support in implementing solutions. |
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A radar model of asteroid Kleopatrashows a distinct "dog bone-shape" of the 217 x 94 km big object which has "the most unusual shape we've seen in the solar system," according to radar astronomer Steve Ostro - it's an apparent leftover from an ancient, violent cosmic collision: Planetary PhotoJournal, JPL Press Release and Picture Page, Cornell Press Release, SpaceScience, SpaceViews, SpaceRef, RP, BBC, Discovery, Fox, CNN, Space.com, Welt.
NASA changes Mars exploration plansAfter a pair of high-profile Mars mission flops, NASA is rethinking its approach to the Red Planet in an unprecedented review that includes everything from science and technology to management and bureaucracy: AP. The best strategy to search for life: SpaceViews.Eight new very low-mass companions to solar-type starshave been discovered with the Swiss 1.2-m Leonhard Euler telescope at the ESO La Silla Observatory - they have masses (or lower mass limits rather) ranging from below Saturn's to 15 times Jupiter's. This brings the total number of such objects to over 40, with 34 companions being very likely planets with minimum masses below 5 Jupiters: ESO Press Release, the Swiss search program, Exoplanet Catalog, SpaceRef, AP, Space.com, BBC, SpaceViews, Discovery.Reality of CM Draconis' planet still not established - but the novel method that may have detected it could be promising: Paper by Deeg & al. Hunting Jupiters with the transit method - results from a two-month observing run with STARE, a small aperture, wide-field, CCD-based telescope that delivers high cadence time series photometry on roughly 40 000 stars in a typical field centered on the galactic plane and should be able to detect roughly a dozen Jupiter-sized planets in its existing dataset: Paper by Brown & Charbonneau. Microlensing constraints on the frequency of Jupiter mass planetsThe PLANET collaboration has monitored nearly 100 microlensing events of which more than 20 have sensitivity to the perturbations that would be caused by a Jovian-mass companion to the primary lens, but no clear signatures of such planets have been detected - these null results indicate that Jupiter mass planets with separations of 1.5-3 AU occur in less than 1/3 of systems: Paper by Gaudi & al.Detecting terrestrial planets by microlensing: Paper by Yock. How rare are other Earths? If our search for life and worlds elsewhere has taught us anything thus far, it is that our world is both rare and common: SpaceRef. Fellowships awarded for planet hunting: JPL. |
Green Bank Telescope nears completionThe last of 2004 aluminum surface panels was recently installed on the 100 m x 110 m collecting dish of the new radio telescope in West Virginia that replaces the one that collapsed in 1988 - science with the GBT should start in early 2001: NRAO Press Release.Casting of 2nd LBT 8.4 meter mirror will begin on May 13th: a Press Release and how the mold was prepared. "Cangaroo II" gamma ray telescope to begin operation in the Australian outback on a former rocket range at Woomera: Homepage, Press Release, BBC, CNN, Space.com, RP. The missing link: early methane ("T") dwarfsThree cool brown dwarfs have been discovered with the SDSS which fall in the effective temperature gap between the latest L dwarfs currently known, with no methane absorption bands, and the previously known methane (T) dwarfs, whose spectra are dominated by methane and water - these stars form part of the brown dwarf spectral sequence and fill in the large gap in the overall spectral sequence from the hottest main sequence stars to the coolest methane dwarfs currently known: Paper by Leggett & al., RAS and JAC Press Releases, SpaceRef, Space.com, Discovery.A candidate substellar companion to HR 7329 with a mass of less than 50 Jupiter masses: Paper by Lowrance & al. On Mir, heat can flow the other wayHeat always flows 'downhill', from hot regions to cold, but French and US scientists have succeeded in reversing this dictum - during an experiment on the space station: Nature Science Update.Struggle over SRTM data rights continuesAs unveiled by the Cosmic Mirror (Update # 174 lead), there were conflicting views about the data rights for the Shuttle Radar Topography Mission - would the German scientists involved in the mission get access to the digital elevation models of the Earth with the highest spatial resolution? Months after the mission the situation has still not been clarified: DLF.No new island was discovered during the SRTM as had been claimed in German media (see last Update micro items): During the STS-99 crew tour in Cologne, Germany, on May 5, SRTM astronaut G. Thiele has now withdrawn that claim that he himself had gathered from an ill-informed newspaper article.
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Compiled and written by Daniel Fischer
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