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Comet Juels-Holvorcem near 6m in evening, morning sky making a slow trek toward the horizon through the constellations Cepheus, Lacerta, and Andromeda: S&T, Ast., Aerith page, recent estimates.

Update # 251 of Friday, March 28, 2003

Meteorites shower Chicago's south suburbs / Progress in solving the GRB mystery / Hot Jupiter observed evaporating

Meteorites shower Chicago suburbs, damage homes Sky watchers in several US states were startled just after midnight on March 27th when a brilliant fireball streaked across the sky and exploded. It was a small (perhaps less than a few meters wide) rocky asteroid with a mass of about 10 metric tons. Some 500 fragments scattered over a 10-km wide zone in the suburbs south of Chicago. Meteorites struck houses, cars, roads, but no people. Such fireballs are surprisingly common: Researchers expect an asteroidal object one meter in diameter or larger to strike Earth's atmosphere about 40 times per year. Few are seen, however, because they usually appear over unpopulated areas - the March 27 event, in contrast, was widely observed. "I heard a detonation," says Lawrence Grossman, a Professor in Geophysical Sciences - and meteorite expert! - at the University of Chicago, who lives in the south suburb of Flossmoor, Ill.: "It was sharp enough to wake me up." Steven Simon, a Senior Research Associate in Geophysical Sciences, lives in nearby Park Forest, where much of the meteorite fell. Simon, who works in Grossman's laboratory, started immediately to collect information from area residents who brought samples of the meteorite to the Park Forest police station. Grossman said meteorites from the fall have been found in Park Forest, which is approximately 30 miles south of downtown Chicago, as well as the nearby communities of Steger to the south and Olympia Fields to the north. He said the meteorite is classified as a chondrite, a common type of meteorite.	U Chicago PR and CCNet's first collection of articles. More coverage by AP, Chic. Tribune, NWI Times, WBBM, Dayton DN, KC Star, Pantagraph, PhillyBurbs, Local 6, ABC Local, RP, Welt, CENAP, AP (in German). Tsunami hazard from impacts overrated? A workshop developed a consensus on the order of magnitude of this hazard, which is substantially less than was estimated years ago - however, the group did not support the position taken by Jay Melosh that tsunami from such small impacts do not pose any hazard whatever: NEO News. Earlier: a UA PR and Melosh's complete Abstract [item 3].
Progress in solving the mystery of Gamma Ray Bursts Several intriguing observations during three GRBs observed in 2002 seem to confirm that these tremendous explosions are linked to supernovae involving particularly massive stars and to the formation of a black hole in the process, though lots of details remain elusive. Also, the new European gamma-ray satellite INTEGRAL has become a crucial contributor to the hunt for GRBs. Supernova remnant emission lines in a particularly good X-ray spectrum of a GRB strengthen the SN-GRB link: Chandra was able to obtain an unusually long observation, about 21 hours, of the afterglow of GRB 020813. A grating spectrometer aboard Chandra revealed an overabundance of elements characteristically dispersed in a supernova explosion. Narrow lines due to silicon and sulfur ions were clearly identified in the X-ray spectrum, which thus supports two of the most important features of the popular supra-nova model for gamma-ray bursts: An extremely massive star likely exploded less than two months prior to the gamma-ray burst, and the radiation from the gamma-ray burst was beamed into a narrow cone (as evidenced by the narrowness of the spectral lines). Strange bumps in the optical light curve of a GRB have been seen during the particularly well observed early fading of GRB 021004: The light from the burst faded only slowly and fluctuated on a timescale of 15 to 30 minutes. And over the course of several hours, the brightness of the afterglow repeatedly decreased and increased - though several models can help explain the surge of energy at the start of the blast and minor surges in the middle, no single model has been found to explain this extra energy during fading. More detailed work is needed before a completely accurate model emerges and suggests accounting for energy distributions in future models. (Fox & al., Nature 422 [March 20, 2003] 284-6) High - and highly variable - polarization in the light from a GRB has been seen with the with the MMT 6.5-meter telescope at Mount Hopkins, Arizona, while observing the afterglow of GRB 020405: Data from this burst indicated a polarization level of almost 10 percent at one point, the highest level ever measured. A day later, a second group measured a polarization level of about two percent. Interestingly, astronomers also observed a two percent polarization only hours before the 10 percent measurement, implying a rapid change in polarization on either side of the peak. What that all means is not so clear. Meanwhile ESA's Integral satellite is detecting gamma-ray bursts at a rate of nearly one per day, establishing itself as a key player in the hunt for these enigmatic explosions. With its four main instruments, the satellite helps locate bursts for follow-up study in two primary ways. The anti-coincidence system of one of its instruments (which usually helps eliminate background noise) can detect a gamma-ray burst almost anywhere in the sky and does so about every day. Integral shares this information with other gamma-ray detectors that comprise the Interplanetary Network: Together, these simple detectors, which are located on spacecraft across the Solar System, pinpoint the location of a burst through triangulation. About once a month, however, a gamma-ray burst goes off within Integral's field of view. Integral has detected four bursts this way dead on, exactly as predicted. The most recent burst (GRB 030227) triggered very many follow-up observations. Integral can provide a unique perspective for those gamma-ray bursts caught directly in its field of view because it can view the bursts rapidly with four instruments. These instruments are an imager, a spectrometer, an X-ray monitor, and an optical camera. All of them observe the same region of the sky simultaneously.	SN-GRB link: Chandra PR [SN], Ast. Slow fade & polarization: CfA, Caltech, GSFC and NASA Releases, S&T, SciAm, PhysWeb, Rtr, SC, ST, BdW, NZ. INTEGRAL: ESA Science News. Winds from Central Engines important for galactic chemistry Supermassive black holes might help seed interstellar space with the elements necessary for life, such as hydrogen, carbon, oxygen and iron - Chandra observations show high-speed winds blowing away copious amounts of gas from the cores of two quasar galaxies: PSU Press Release, BBC, SC, NZ. Subaru sets galaxy distance record: z=6.58 The Japanese Subaru telescope has found a galaxy at a redshift of 6.58, the most distant galaxy ever observed (the previous record was 6.56) - this discovery is the first result from the Subaru Deep Field Project, during which approximately 70 distant galaxy candidates were found: Subaru PR, Ast., BBC. Chandra look into Lockman hole shows 'adolescent' Universe about five billion years ago when the familiar web-like structure of galaxy chains and voids first emerged: Chandra Release. Very distant quasar center measured at 3 billion solar masses The measurement involved the spectrum of a quasar with a redshift of 6.41 - the supermassive central engines thus formed extremely early: JAC Press Release, SC, BBC, AFP, NZ. Comeback for the 'intermediate-mass black holes'? New observations may confirm the existence of black holes with a few 100s of solar masses: CfA, NASA Releases, S&T, Ast., SciAm, NZ.
Hot Jupiter observed evaporating under its Sun's heat Using the Hubble Space Telescope, for the first time, astronomers have observed the atmosphere of an extrasolar planet evaporating off into space. Much of this planet may eventually disappear, leaving only a dense core. The planet is a type of extrasolar planet known as a 'hot Jupiter'. These giant, gaseous planets orbit their stars very closely, drawn to them like moths to a flame. The scorched planet called HD 209458b orbits 'only' 7 million kilometres from its yellow Sun-like star and was the first one observed to transit the disk of its sun (see Update # 158 story 3), which allows for probing its atmosphere (see Update # 230 small items) as well as any gases in its vicinity. The HST observations with the STIS spectrograph have now revealed a hot and puffed-up evaporating hydrogen atmosphere surrounding the planet. This huge envelope of hydrogen resembles a comet with a tail trailing behind the planet. The planet circles the parent star in a tight 3.5-day orbit. Earth also has an extended atmosphere of escaping hydrogen gas, but the loss rate is much lower. The planet's outer atmosphere is extended and heated so much by the nearby star that it starts to escape the planet's gravity. Hydrogen boils off in the planet's upper atmosphere under the searing heat from the star. Astronomers estimate the amount of hydrogen gas escaping HD 209458b to be at least 10,000 tonnes per second, but possibly much more. The planet may therefore already have lost quite a lot of its mass.	The full paper by Vidal-Madjar & al. in PDF format, ESA HST and U of A News, and coverage by ST, S&T, Ast., NYT, UPI, AFP, SF Gate, SC, RP, NZ. A possible new transiting planet A very low velocity variation (<500m/s) of the host star OGLE-TR-3 may be caused by its unseen companion - if confirmed, this makes OGLE-TR-3 and OGLE-TR-56 (see Update # 247 story 3) the first extrasolar planets discovered via their transit light curves: paper by Dreizler & al. "First Light" for HARPS at La Silla - an spectrograph, built especially to detect exoplanets with an unequalled precision of 1 m/s, has passed its first tests with flying colors: ESO PR.

STS-107/ISS Update A data recorder from Columbia has been found, with the tape recording of tons of reentry measurements in good quality (it will be read out soon), while the orbiter's final minutes are also being reconstructed on the basis of 19 amateur videos of the reentry: ESA Tech Update # 4 on the investigation, the data recorder, a related CAIB Press Release (earlier), tons of debris pictures & analysis, viewgraphs on the search, the status of Columbia's reconstruction, the Mar. 11 CAIB PC transcript, the merged timeline (many updates) [NASA version], what Daugherty really thought (complete PC transcript), a Return-to-Flight Roundtable, Pettit's ISS Chronicles and the ISS Picture of the Day (e.g. of an Iridium flash!), Science@NASA on astrophotography from the ISS, NASA Releases on the the search for debris and a newly formed NASA Accident Investigation Team (NAIT), an ESA Release on ISS' Columbus and coverage of Mar. 28: New Sci., SC, NYT, AP, RP. Mar. 27: SR, FT 4, 3, 2, 1, WP, SC 2, 1, NYT, CNN, AFP, ST 2, 1. Mar. 26: SR, SN, WP 2, 1, NYT, SC, Rtr, ST 2, 1, UPI, SC, ARRL, NZ. Mar. 25: TX Monthly, New Sci., SN, WP, FT 4, 3, 2, 1, UPI, ST, SC 2, 1, AP, NYT 2, 1, NZ.

Mar. 24: AW&ST [abstract], SN 2, 1, FT 2, 1, Dsc 2, 1, Rtr, AP, SR. Mar. 23: WP. Mar. 22: FT 4 [SC], 3, 2, 1, WP, AP, ST, Welt. Mar. 21: SN, WP, NYT, SC. Mar. 20: WP, NYT, SC, AFP, UPI, BBC, ST, NZ. Mar. 19: SN 2, 1, SC, FT 3, 2 1, AP, AFP, ST. Mar. 18: SN, WP, NYT, SC 2, 1, FT 2, 1, ST. Mar. 17: WP, FT 2, 1, SpaceRev, SC, UPI, Rtr, AFP, Welt. Mar. 16: ST 3, 2, 1, WP, AFP 2, 1, SC. Mar. 15: FT 3, 2, 1, WP 2, 1, NYT, ST 2, 1, SC. Mar. 14: New Sci., SN, FT, SC, WP 2, 1, SC 2, 1, NYT 1, Dsc, ST, AFP, UPI, BBC, RP, NZ 2, 1. Mar. 13: SN, NYT, AFP, UPI, BBC, SC, ST. Mar. 12: AD, WP, NYT, FT, UPI, NZ. Mar. 11: SN 2, 1, Wired, FT 2, 1, ABC, UPI, WP 3, 2, 1, AFP 3, 2, 1, WT, NYT 2, 1, SC, NZ 2, 1. Mar. 10: SN, SD, AP, NYT, BBC, AFP, SC 4, 3, 2, 1, ST, NZ. Mar. 9: SN, ABC, NYT 2, 1. Mar. 8: SN, WP 2, 1, FT, AP, Rtr, NYT, SC, ST, NZ. Mar. 7: SN, AFP, UPI, FT 5, 4, 3, 2, 1, SC 2, 1, WP 2, 1, NYT 2, 1, CSM, ST, NZ, Welt. The Orbital Space Plane (OSP) Level I Requirements Program Interpretation Document: Text version. OSP idea questioned: ST. Shenzhou carries military payload, too, says the human spaceflight application system commander at the Chinese Academy of Sciences: SD. Meet the first astronaut: BBC. China's plans: NYT, Welt. No Chinese Mars missions in sight: SD, ST.

Japan launches its first recon sats A Japanese H-2A successfully launched on March 28 that nation's first two military reconnaissance satellites - one of the two Information Gathering Satellites (IGS) 1a and 1b is believed to have a camera capable of taking images with a resolution of about one meter per pixel, while the other has a synthetic aperture radar system: SN, SD, NYT, ST, BBC, AFP (other, earlier, still earlier stories), Guardian, AP, NZ. Still three options possible for Rosetta It's either to Churyumov-Gerasimenko or to Wirtanen, perhaps even on a Proton as indicated in Update # 249 - and the decision will be made in May: ESA News, SN (includes options for SMART-1 as well), SD, Plan. Soc. Earlier rumors: New Sci., ST, BBC, SD, NZ, Welt. Ariane's next flight: NZ. MESSENGER assembly under way - the Mercury mission will launch one year from now: Status. Launch of Mars Express delayed by about 10 days to no earlier than June 6, due to a problem with a component - replacing the unnamed component is "not a big deal": New Sci., BBC, AFP, ST. Spacecraft shipped to Baikonur: ESA Release. France's Netlander delayed to 2009: JPL. Experiment ideas for proposed 2009 ESA Mars mission sought: ESA Release, ST, BBC. Fleet of Mars rovers getting ready - and facing last minute problems: MER Status, Cornell PR, FT (earlier), NYT, CSM. Gray hematite at the primary landing site: AstroBio., PSRD. Mars is somewhat dangerous to your health (and other Mars Odyssey insights): JPL Release, S&T, SC (other story), BBC, FT, ST. Water flowing on Mars - today? Dark streaks on crater and valley walls may indicate that brackish water currently flows across the surface of Mars: BBC, SC. Clusters of craters on Mars may be created by rocks launched from the planet's own surface: Ast. Why one must observe Mars this summer - it's coming closer than in millennia: ArkSky Observing Guide, Celestial Delights Obs. Guide, UPI. Launch of GALEX delayed to 2nd half of April Workers will install debris shields inside the Galaxy Evolution Explorer telescope, pushing its launch to the second half of April, because NASA is worried that bits of hardware might be loose inside the spacecraft: FT. Artemis supports Envisat - the first satellite-relayed images from Envisat have been received via the Artemis data-relay spacecraft: ESA Release, New Sci., NZ. Burning Iraq oilfields as seen by NOAA and Terra. Sat pix of Iraq for sale: AP. SIRTF has arrived at the KSC The Space Infrared Telescope Facility arrived on March 6 at the Kennedy Space Center to begin final preparations for its launch - probably on April 18 - aboard a Boeing Delta II rocket: JPL, Cornell, KSC and NASA Releases, AFP, SC. Vanguard satellite now 45 years in orbit - the small satellite has made more than 178,000 revolutions of the earth and traveled some 9 billion km: NRL Press Release. And 35 years ago Yuri Gagarin died in a plane crash that is raising questions even today: AFP. Yuri's night 2003: SD. Galileo navsat crisis solved! The European satellite system to compete with the United States' Global Positioning (GPS) network came closer to reality on March 28 when the German and Italian governments settled differences that had threatened to sink the project: AFP (earlier), Rtr, ST, NZ. Earlier: ST (earlier), ZEIT. No global GPS blackout expected during the Iraq war, DoD promises: New Sci., NZ. New GPS sat to launch: SN. Iraq jamming GPS signals? AFP. It won't help: AFP. Pretty pictures The HST image sequence of the light echo around V838 Mon - already known from Update # 249 (micro-items) - has now been released in full resolution: HST, ESA, NSF, RAS, NASA Releases, UA News, APOD, S&T, UPI, SC, RP. A new analemma photograph with 38 exposures, this time set over Delphi: APOD. A Hubble view of M 57, the Ring nebula: APOD. A SNR as seen by Chandra, a textbook example of the double-shock structure in DEM L71: MSFC Release, S&T, Ast. A digital image of the Earth that has been widely misrepresented as a real one: APOD. Star Trails over Kilimanjaro in a 3½-hour exposure: APOD.

2MASS survey completed, data released The vast archive of images and data resulting from the Two Micron All-Sky Survey (2MASS), the most thorough, high-resolution survey of the sky, has been completed - the archive, which features some five million images, is now available online for scientists and sky watchers: U Mass, JPL Press Releases, PhotoJournal, gallery, AP. Exact sizes of the three closest stars measured - and the VLTI data about Alpha Centauri A, B and C confirm the theoretical values based on asteroseismology: a paper by Kervella & al., an ESO Press Release and coverage by SC, NZ. NASA selects aurora science mission NASA has selected a mission to study the geomagnetic storms that create aurorae - the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission will be the next Medium-class Explorer (MIDEX) mission, consisting of 5 small satellites scheduled for launch in 2007: NASA, Berkeley Releases, Ast., ST. UK satellite to study Sun's role in climate in Britain's first solo space science mission in 20 years - the Earthshine mission should provide vital data on climate change: BBC, ST. Solar power rising slightly for the last quarter century - but also for more time? If so, its role in global warming could have been (somewhat) greater than thought: NASA, GSFC Releases, SC. Double eruptive prominence: GSFC (plus the best CMEs of 2002). Switch from GOES-8 to -12 on April 8: NOAA Notice. Pular emission from region measuring 60 cm Powerful radio bursts in pulsars are generated by structures as small as a beach ball - these are by far the smallest objects ever detected outside our solar system: NRAO Press Release, Ast., New Sci., UPI, SC, NZ. Construction of ANTARES neutrino detector starts in earnest in the Mediterranean: SC. Virtual Observatory catches Brown Dwarf during trial run Scientists have discovered a new brown dwarf, and they weren't even trying - an early demonstration of what will be the National Virtual Observatory (NVO) yielded the surprising bonus, when two separate databases of sky objects were 'mined' in an attempt to confirm the existence of already-known brown dwarfs as a feasibility demo: JHU Press Release, Ast. SRTM radar map reveals Chicxulub crater The Shuttle Radar Topography Mission has provided the most telling visible evidence to date of a 180 km wide, 900 m deep impact crater, the result of a collision with a giant comet or asteroid 65 Myr ago: JPL Release, picture, NatGeogr, UPI, SC, BBC, Ast., Heise. Why are there so few lunar meteorites? They should outnumber the Martian ones 100:1, but they don't: S&T. Five times more water on the Moon? NSU. Honduran moon rock taken from 'owner': NASA Note, BBC, CollectSpace. Another 4 new moons of Jupiter have been announced by the Hawaiians, raising the tally to 52: Press Release, ST, Ast., SC. Great Dark Spot found on Jupiter by Cassini: Science@NASA, APOD. Jupiter's weather gets clearer: S&T, Ast. Galileo views changing Io: Ast. Patrick Moore has turned 80 - he is best known for The Sky at Night, a BBC program he has broadcast every lunar month since April 1957: S&T, Rtr. Cosmology after WMAP - a somewhat critical review in Science. Strange topology, fate of the Universe? Paper by Uzan & al., NYT, Welt (fr�her). Quantum trouble claims (see Update # 249 story 2 sidebar 5) also back: UAH Press Rel., SC, NZ. A new ESO website on the transit of Mercury this May 7 - a dress rehearsal for the transit of Venus in 2004: Special Page. Earth's magnetic field to flip? Something unexplained is happening to the Earth's magnetic field in recent years: BBC, ZEIT. VISAR video enhancing software wins NASA prize - law enforcement officers are seeking the help of two NASA scientists who study the Sun and storms like hurricanes: Science@NASA. Lumicon returns - astronomy company will be back in late April: S&T, Ast. Reading the weather from the sky, i.e. from atmospheric-optical effects: SC. Space myths, hoaxes: SC. 166 SETI@home sites checked with Arecibo telescope; no aliens found: Plan. Soc. story (earlier), BBC, AP, NZ. Earlier: Plan. Soc. PR (earlier), Berkeley PR, "Stellar Countdown", NSU, New Sci., Wired, UPI, Ast., SC, BBC, ST, Welt, NZ.

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