Monday9 February 20046:29pm MST2004-02-10 UTC 0129 back top next  

The Asteroid/Comet Connection's
daily news journal about
asteroids, comets, and meteors


Today's issue status: done
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Cover: PHA 2004 CL was announced overnight in MPEC 2004-C34 as discovered by Bruce Koehn at LONEOS in Arizona early Saturday, and confirmed over the next night by Gnosca and Great Shefford observatories in Europe, and by Sandlot, Sabino Canyon, and Tenagra II observatories in the U.S., and also by Robert Hutsebaut working in Europe but running a Rent-a-scope telescope in the U.S., at New Mexico Skies Observatory. The image at left is an enlarged stack of three sets of twelve 20-second exposures (36 total) used to determine his first position, at 10:33 Sunday morning in Brussels. From its brightness, 2004 CL is estimated at about 225 meters/yards wide.

News briefs – part 1/2 Major News for 9 Feb. 2004 back top next  
News briefs

Meteor news:  The Otago Daily Times of New Zealand has an article today, "Meteorite sparks fears of boat fire," with one witness reporting a "bright orange light" off the North Otago coast at 10:45pm.

Wabar Craters:  Arab News of Saudi Arabia has an article today, "Wabar Crater Under Threat From Vandals," describing problems with trash dumping, graffiti, and tourism at what is described as "One of Saudi Arabia's greatest geological wonders, [the] crater stretches over 2 km from rim to rim, far bigger than the meteor impact site that is a major tourist attraction in Arizona." Huh? The entire Wabar Craters site, isolated deep in Saudi Arabia's Empty Quarter (Rub al-Khali), encompasses multiple impact features in an area about a kilometer across at its widest, and is not nearly so spectacular in appearance as the photo with this article. What in fact is shown and talked about is Wahba Crater, a volcanic feature described as "halfway between Jeddah and Riyadh" on David Bunyard's impressive Wahba Crater photo page.

For more about the real Wabar, see the USGS Wabar Meteorite Impact Site page by Jeff Wynn and Gene Shoemaker, David Weir's Wabar meteorite page, and Wikipedia's Wabar craters entry. This impact site was revealed to science in 1932 and has been associated with an 1863 fireball, but may be a bit older. David Weir notes that, of "nearly 200" known Earth-impact sites, "Wabar Crater is one of only seventeen to contain remnants of the original impacting object."

That object was probably too small to be officially categorized as "potentially hazardous" if it were to be spotted in space today. A USGS 19 October 1998 news release says that it is believed to to have broken into four or more pieces upon atmospheric entry, with the largest "between 8 and 9.5 meters in diameter [striking] with a force comparable to the Hiroshima nuclear blast." (Many pages on the Wabar Craters have defunct links to a great Wynn-Shoemaker Scientific American article. It is available as a 603Kb PDF from Keith Meldahl at MiraCosta College.)

more News briefs >>

News briefs – part 2/2 Major News for 9 Feb. 2004 back top next  

<< continued from part 1

No-so-close call:  Speaking of incoming small objects (Wabar, above), observers late UT one night last month — Tuesday the 13th — thought they might have a live one. Peter Birtwhistle tells about it on his 2004 AS1 page, with a nice animation from his observations of this object on January 29th.

JPL today puts 2004 AS1's absolute magnitude at H=20.29, which by standard formula converts to a diameter of 230 to 520 meters/yards, with 295 as best guesstimate. And it is now known that it will pass Earth on February 16th at just over 33 lunar distances (LD), and doesn't ever come closer than 8.56 LD. However, at the time it was posted to the Minor Planet Center's NEO Confirmation Page (NEOCP) with LINEAR discovery designation AL00667, this object was thought too small to be hazardous. As Spaceguard U.K. put it: "probably smaller than a bus, and would certainly never make it through the atmosphere to hit the ground." And, Peter Birtwhistle reports, "The original MPC ephemeris . . . showed that in 27 hours time the object was predicted to impact the Earth."

But no one was able to find it where predicted by that ephemeris, and it wasn't until LINEAR picked it up again about 24 hours after discovery that a better ephemeris became available, and the hunt could succeed and worries could be set aside.

The NEOCP has since undergone a number of improvements to help deal with various problems encountered in the course of this matter.

Hubble:  Space.com has an article today, "Heads Up! Debate over Deorbiting Hubble," that tells about the risks of uncontrolled re-entry for man-made objects with pieces large or dense enough to hit Earth's surface.

Today there are articles at both Space.com and New Scientest about the renewed debate over NASA's decision to forego further servicing missions to the Hubble Space Telescope. See A/CC's report yesterday for more links.

Risk monitoring - part 1/1 Major News for 9 Feb. 2004 back top next  
Risk monitoring 9 Feb.

Today's Daily Orbit Update MPEC carries observations of 2004 CB from McCarthy and Tenagra II observatories in Connecticut and Arizona yesterday morning, and from Great Shefford Observatory in England early today. Both NEODyS and JPL today cut their impact solution counts and raised their overall risk ratings slightly for this object.

Summary Risk Table - sources checked at 0018 UTC, 10 Feb

Object

Assessment

Years

VI
PS
cum
PS
max
T
S
Arc 
days
 2004 CB NEODyS 2/92019-20769-2.86-3.3605.687
JPL 2/92034-209510-2.60-2.9005.687
 2004 BN41JPL 1/312086-20982-6.57-6.6906.998
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.
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