Presentation Abstract

Title The Extraordinary Disrupting Asteroid P/2010 A2
Author Block David Jewitt1, H. Weaver2, J. Agarwal3, M. Mutchler4, M. Drahus1
1UCLA, 2Applied Physics Laboraory, Johns Hopkins University, 3ESA-ESTEC, Netherlands, 4STSCI.
Special Instructions It would be nice to pair with Jessica Agarwal's talk in the order Jewitt then Agarwal
Abstract P/2010 A2 has the orbit of an inner main-belt asteroid (a,e,i = 2.29 AU, 0.124, 5.3 and Tj = 3.6) but is the source of an extended dust tail that lies near the projected orbit. We used ground-based data to recognize the strange nature of this object, then secured Hubble Space Telescope (HST) observations from January 12 to May 29 2010, in order to ascertain its nature and evolution. Our data show that A2 consists of a leading nucleus, about 120 meters in diameter (albedo 0.15 assumed), followed by a unique, X-shaped structure that is the source of a tail (or trail) of millimeter-sized dust particles. Examination of the tail shows that the particles were emitted in 2009 February/March at velocities less than 1 m/s. The combined mass of material in the tail is roughly equal to the mass of a single 12-meter radius sphere. Spectroscopic observations from the Gemini North telescope show no evidence for CN or other optical gas lines.
We consider it unlikely that ice exists in such a small, warm object so close to the inner edge of the asteroid belt. Thus, while A2 technically meets the definition of a main-belt comet, we believe its activity has another cause. We interpret A2 as a debris cloud from a small, previously unknown asteroid that has been impacted by a still smaller body. Alternative explanations will be discussed.

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42nd DPS Program published in BAAS volume 42 #4, 2010.