This story is from UCLA Today, a discontinued print and web publication.

'Comet' turns out to be debris from asteroid collision, something not seen before

NASA's Hubble Space Telescope has observed a mysterious X-shaped debris pattern and trailing streamers of dust that suggest a head-on collision between two asteroids. Astronomers have long thought the asteroid belt is being ground down through collisions, but such a smashup has never been seen before, a NASA news release says.
The comet-like object imaged by Hubble, called P/2010 A2, was first discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) program sky survey on Jan. 6. New Hubble images taken on Jan. 25 and 29 show a complex X-pattern of filamentary structures near the nucleus.
"This is quite different from the smooth dust envelopes of normal comets," said principal investigator David Jewitt of UCLA's Department of Earth and Space Sciences. "The filaments are made of dust and gravel, presumably recently thrown out of the nucleus. Some are swept back by radiation pressure from sunlight to create straight dust streaks. Embedded in the filaments are co-moving blobs of dust that likely originated from tiny unseen parent bodies."
Hubble shows that the main nucleus of P/2010 A2 lies outside its own halo of dust. This has never been seen before in a comet-like object. The nucleus is estimated to be 460 feet in diameter.
At the time of the Hubble observations, the object was approximately 180 million miles from the sun and 90 million miles from Earth.
Media Contact