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Friday5 December 200310:27pm MST2003-12-06 UTC 0527
Today's news about Asteroids, Comets & Meteors
Page status: done & updated
  • News briefs – flyby today & readings on Yarkovsky effect, Mahuika Crater & more plus meteor news
  • Risk monitoring – JPL has removed 2003 WY153 & NEODyS has posted 2003 XM
Intruder:  In the midst of an observing effort to follow one small object making a close flyby today (see immediately below), another was found coming even closer. 2003 XJ7 was announced in MPEC 2003-X30 at 0230 UT as discovered Friday morning by LINEAR and confirmed early Saturday morning UT by Great Shefford Observatory, with an absolute magnitude that converts to a width of roughly 25 meters/yards. The MPEC doesn't note anything special about this object, but Reiner Stoss tells A/CC that it will fly past at about 0.4 lunar distance on Saturday, which puts it in the all-time top-ten closest flybys, the second or third closest this year, and the largest object of those three. The Observatorio Astronomico de Mallorca (OAM) caught XJ7 since the MPEC, and many more observations could come in overnight as observers around the world quickly respond.
News briefs

Flyby today:  MPEC 2003-X28 overnight announced 2003 XV, which, from its brightness, is roughly estimated at 12-27 meters/yards wide. It was discovered early Monday by Robert McMillan with the Spacewatch 0.9m telescope and quickly followed up by Powell Observatory, but not seen again until found in LINEAR images from yesterday morning. Kyle Smalley footnoted the MPEC with, "This object will pass .0031 AU from Earth at December 7.00 UT." Today's Daily Orbit Update MPEC carries 2003 XV observations from JPL's Table Mountain Observatory this morning.
Animation of 2003 XV Earth-Moon encounter
today, by Pasquale Tricarico using ORSA Pasquale Tricarico calculates passage at 1.19 LD from Earth at Dec. 6.95 (around 5:45pm EST today) after passing 1.05 LD from the Moon at Dec 6.58 (around 9am EST), and provides this illustration from his ORSA software for Linux.

Yarkovsky effect:  The journal Science edition for today has an article for purchase, "Direct Detection of the Yarkovsky Effect by Radar Ranging to Asteroid 6489 Golevka," by Steven Chesley et al. New Scientist posted a report yesterday, "Sunlight's gentle nudge on asteroids detected," and Scripps Howard News Service has a wire story from yesterday, "Sun can push asteroids closer to Earth." Some other scientific papers about the Yarkovsky effect are available from co-author David Vokrouhlicky, and see A/CC's links for more info. PhysicsWeb has an article today, "Radar reveals asteroid force."

The astronomers also believe that measuring the strength of the Yarkovsky acceleration is the only way to determine the mass and density of small (sub-kilometre) asteroids from Earth. . .  "Never before has the mass of a small solitary asteroid been measured," Chesley told PhysicsWeb. . .  "In this case it suggests that the asteroid has a heavily fractured interior." 

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News briefs, part 2
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Readings:  At last month's meeting of the Geological Society of America, Dallas Abbott et al. announced the discovery of Mahuika Crater on the New Zealand continental shelf (abstract and related). It is described as "202 km wide" and young enough to fit into Edward Bryant's controversial theory connecting aboriginal stories and archaeologic and geologic evidence to a mega-tsunami around 1500 AD. U.S. News & World Report's December 8th edition has an article posted yesterday.

The Litchfield County, Conn. Times has an article today, "A Washington Man Has a Plan for Stargazers," about the Slooh.com Internet telescope project (see more links in news yesterday): "Slooh is also giving away 1,000 annual memberships to schools across the United States. The first 1,000 individuals who sign up for a free trial of Slooh before Dec. 31, 2003 can choose a K-12 school . . . to receive an annual membership."

Astronomy.com has an article today, "Just passing by," about plans for the New Horizons mission to practice its Pluto/Charon flyby during its gravity-assist passage through the jovian system (see more links).

Meteor news:  SpaceWeather.com is reporting about this year's Leonids:

Between Nov. 13th and Nov. 23rd, Earth encountered three (and possibly four) dust streams from comet Tempel-Tuttle. While forecasters generally overestimated peak meteor rates, the total number of Leonids counted in mid-November exceeded predictions by a factor of two. This activity was spread out over many days and so attracted little notice. 

This comes from Bill Cooke at NASA's Marshall Space Flight Center, whose brief report is available as a 131Kb PDF.


Risk monitoring 5 Dec.

The Friday Daily Orbit Update MPEC (DOU) has observations of 2003 WY153 from yesterday morning from Tenagra II Observatory, and today JPL removed this object from its Current Impact Risks page, while NEODyS very, very slightly raised its low-rated WY153 assessment.

Last evening in Pasadena, JPL posted 2003 XL and 2003 XM (see "Risk monitoring" for yesterday). Today's DOU has observations of 2003 XM from LINEAR yesterday morning that extend XM's observational arc by 31 minutes. At last check JPL hasn't updated on this data. This evening in Pisa, NEODyS posted 2003 XM, too, but with more impact solutions and higher risk ratings.

The arc didn't get extended for elusive 2003 WT153, but the DOU has new data from Whipple Observatory from Monday morning. Today JPL's impact solution count grew and its low risk assessment for this tiny object rose slightly. And NEODyS doubled its count of WT153 impact solutions while raising its overall risk assessment.

Summary Risk Table - sources checked at 0015 UTC, 5 Dec

Object

Assessment

Years

VI
PS
cum
PS
max
T
S
Arc 
days
 2003 XM NEODyS 12/52009-207227-3.74-4.4401.103
JPL 12/52053-20531-5.31-5.3101.083
 2003 XLJPL 12/52096-20992-5.44-5.6001.076
 2003 WY153JPL 12/5R E M O V E D
 NEODyS 12/52071-20711-7.46-7.4605.112
 2003 WW26 NEODyS 12/12061-20725-3.91-4.1708.925
JPL 12/12061-20613-3.90-4.1508.925
 2003 WT153 NEODyS 12/52043-208036-6.61-6.9902.501
JPL 12/52044-210340-6.75-7.4102.501
 2003 WGJPL 12/52055-20551-6.10-6.10010.779
NEODyS 11/29R E M O V E D
 2003 WD158 NEODyS 12/32035-208032-5.57-6.6702.083
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.

Without new observations, JPL today slightly lowered its 2003 WG risk assessment.

The MPC Last Observation page is showing that new observations are in from this morning for 2003 WD158 and 2003 WY153, and also 2003 WW26 from yesterday.


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