37th DPS Meeting, 4-9 September 2005
Session 3 Asteroids I
Oral, Monday, September 5, 2005, 11:00am-12:30pm, Law LG19

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[3.06] Probing the Depths of the Solar System: A Tale of Two Asteroids

D. J. Tholen (Univ. of Hawaii), F. Bernardi (Univ. Hawaii), R. A. Tucker (Univ. Arizona)

Our survey of small solar elongations has produced several near-Earth asteroid discoveries in recent months. Two are of particular interest and will be the focus of this year's presentation.

2004 XZ130 was discovered on 2004 December 13 UT and followed through 2005 February 8 UT. The resulting 27 astrometric observations allow an orbit to be computed that yields an aphelion distance of 0.898 AU, the smallest known for any asteroid. The semimajor axis of 0.618 AU, also the smallest known for any asteroid, places the object very close to the 2:1 resonance with the Earth, which will make its recovery quite straightforward late this year. Given that 2004 JG6 also has a similar semimajor axis, it seemed worthwhile to explore the stability of the resonance. It was found that interactions between 2004 XZ130 and Venus dominate over any resonance with Earth; in fact, one of the sample integrations produced an approach to Venus of 1.1 Venus radii about a quarter million years from now. The higher inclination of 2004 JG6's orbit helps to protect it from Venus interactions, and it was found to spend more time trapped in the resonance.

On 2004 June 19 UT, we discovered 2004 MN4 at a solar elongation of 56 deg. The object was subsequently recovered at 70 deg elongation by the Siding Spring Survey, and then precovered at an elongation of 68 deg by Spacewatch. An examination of the visibility of this Aten-type object shows that it spends only 5 percent of the time at elongations greater than 90 deg for the 20 year period centered on the discovery date. In 1998 it reached a V magnitude of 14 with a maximum elongation in excess of 100 deg, but nobody discovered it. It is now known that the object will pass about 35000 km from the Earth on 2029 April 13, which is within the belt of geosynchronous satellites, and possibly as close as 27000 km. This 0.5 km diameter object was the first to reach level 4 on the Torino Scale, and reinforces the importance of conducting NEO surveys at small solar elongations.

This work was funded by the NASA Near Earth Objects Observation program.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.