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Wednesday31 December 20034:58pm MST2003-12-31 UTC 2358
Today's news about Asteroids, Comets & Meteors
Page status: done
  • Stardust – NASA reports the spacecraft is now within 81P/Wild 2's coma
  • Fractured chronicles – puffy white comets & stellar-core asteroids
  • Risk monitoring – JPL posts 2003 YK118 & YH136 while NEODyS removes 2003 YG118

The University of Chicago has a news release today, "University of Chicago instruments to reach comet, Mars in same busy week." And Astrobiology Magazine has an interview today with the Stardust mission's principal investigator, Donald Brownlee, "Extraterrestrial Capture." Brownlee was at the NASA/JPL news conference yesterday, about which Reuters put out a wire story late yesterday, "NASA Probe Heads for Close Encounter with Comet," and the Rocky Mountain News has an article today, "Wild chase gooses scientists."

NASA headquarters issued a news release today, "NASA Spacecraft Has Shields Up," reporting that, at 48 hours from the 2:40am EST January 2nd flyby of 81P/Wild 2, the Stardust spacecraft "has officially entered a comet's coma," which means particles could be encountered now at high velocity, so the vehicle has been turned to fly with its Whipple Shields facing forward into the onslaught.

Fractured chronicles

A Houston Chronicle article about the Stardust mission yesterday described comets as "puffy white objects [most of which] orbit the sun far beyond Pluto." But that's nothing compared with the tall tale told today at the San Francisco Chronicle about how "The mother of all Quadrantids" — referring to 2003 EH1 — is "the dim burnt-out core of an ancient star":

Last month, astronomer Peter Jenniskens . . . predicted that the source of the meteor shower would eventually be confirmed as the dim burnt-out core of an ancient star that must have exploded in violent brilliance more than 500 million years ago. Now, astronomers on a mountaintop in Chile have just spotted that object climbing high in the southern Milky Way, bang-on exactly where Jenniskens said it should be. The remnant is the equivalent of what's known as a 23rd magnitude star, shining far too faintly for even the best amateur-grade telescopes to pick up. Too dull and puny to be classified as a comet, the object is now only an asteroid, a rock about 2 miles in diameter that is orbiting the sun between Earth and Jupiter. When it was a star that exploded, astronomers theorize, debris flew into solar orbit to create what observers on Earth took to calling the Quadrantid meteor shower. 

See A/CC's item yesterday for links to articles about what's believed to be the real Quadrantids story.


Risk monitoring 31 Dec.

The last Daily Orbit Update MPEC (DOU) for the year 2003 reports observations of 2003 YG118 and 2003 YK118 from LINEAR from early yesterday in New Mexico. Today NEODyS removed 2003 YG118 and JPL's new YG118 risk assessment is down to one low-rated impact solution. JPL has now posted 2003 YK118 and NEODyS, which posted it yesterday, today cut the count of impact solutions while raising its overall YK118 risk ratings.

The DOU doesn't report new data for the other three objects with impact solutions that are currently in view, but the Minor Planet Center Last Observation page is showing that Siding Spring Observatory caught 2003 YD45 and 2003 YE45 yesterday in Australia.

Today the European Spaceguard Central Node Priority List dropped tiny 2003 YS70, which it had put at level 1 "Urgent" and had noted will go out of view for most observers tomorrow.

Summary Risk Table - sources checked at 2214 UTC, 31 Dec




 2003 YS70 NEODyS 12/282057-20808-7.72-8.1504.992
JPL 12/282057-20856-7.97-8.3704.992
 2003 YK118JPL 12/312006-2102108-1.16-1.8402.063
 NEODyS 12/312006-207858-1.27-1.8702.063
 2003 YH136JPL 12/312014-209314-2.60-3.0202.722
 2003 YG118NEODyS 12/31R E M O V E D
JPL 12/312050-20501-4.43-4.43013.056
 2003 YE45 NEODyS 12/302030-20728-3.97-4.0007.997
JPL 12/302043-20431-6.07-6.0707.997
 2003 YD45NEODyS 12/30R E M O V E D
JPL 12/302074-20741-5.90-5.9009.344
VI = count of "virtual impactors" (impact solutions)
See A/CC's Consolidated Risk Tables for more and maybe
  newer details, and check the monitors' links for latest info.
Note that only objects recently in view are shown here.

Update:  JPL has posted 2003 YH136, which was announced today in MPEC 2003-Y98 as discovered on December 28th by LINEAR and followed up by Sabino Canyon Observatory yesterday morning in Arizona and this morning by the Observatorio Astronomico de Mallorca (OAM). JPL puts YH136's diameter at about 560 meters/yards.


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