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Hubble sees aftermath of asteroid smash-up

Posted: October 13, 2010

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Using a sharp-eyed camera installed by space shuttle astronauts last year, the Hubble Space Telescope has spotted a long, glittering tail of dust streaming from an asteroid. Scientists believe the mysterious object was the victim of a collision in the asteroid belt in early 2009.

After the asteroid's discovery by ground-based observatories in the Lincoln Near-Earth Research, or LINEAR, program sky survey, Hubble tracked the object for five months between January and May 2010 with the telescope's Wide Field Camera 3.

The asteroid's distance from Earth was increasing during that period, ranging from 100 million miles in January to 222 million miles in late May.

Hubble's observations convinced scientists the object was not a comet, as first believed, but an asteroid recovering from a violent smash-up in deep space between the orbits of Mars and Jupiter. The debris cloud was arranged in a strange X shape, not the normal signature of an outgassing comet.

Once the object, named P/2010 A2, was found to be an asteroid, scientists thought they were looking at the spectacular remnants of a collision. The tightly-clustered tail of debris had not dispersed, so researchers figured they just missed never-before-seen celestial fireworks.

Further calculations indicate the high-speed impact likely occurred in February or March 2009, but Hubble's images are the first to directly illustrate the aftermath of such an event.

This montage includes four images from Hubble between January and May showing the evolving tail of dust with asteroid P/2010 A2. Credit: NASA/ESA/D. Jewitt (UCLA)
"We expected the debris field to expand dramatically, like shrapnel flying from a hand grenade," said David Jewitt, an astronomer at the University of California in Los Angeles. "But what happened was quite the opposite. We found that the object is expanding very, very slowly."

According to a NASA press release, Hubble resolved a solid object about 400 feet in diameter. Scientists believe the long tail of dust behind the asteroid is made of particles ranging in size from 1/25th of an inch to 1 inch.

Computer models predict modest-sized asteroids collide about once per year, littering the solar system with dust and rock fragments.

"These observations are important because we need to know where the dust in the solar system comes from, and how much of it comes from colliding asteroids as opposed to 'outgassing' comets," Jewitt said.

Observations in our own backyard could also contribute to research in other solar systems.

"We also can apply this knowledge to the dusty debris disks around other stars, because these are thought to be produced by collisions between unseen bodies in the disks," Jewitt said. "Knowing how the dust was produced will yield clues about those invisible bodies."

An analysis of P/2010 A2 indicates a small object about the size of a light truck crashed into a much larger asteroid at about 11,000 mph, unleashing energy equivalent to the detonation of a small atomic bomb, according to NASA.

"Once again, Hubble has revealed unexpected phenomena occurring in our celestial 'backyard," said Eric Smith, Hubble program scientist at NASA Headquarters. "Though it's often Hubble's deep observations of the universe or beautiful images of glowing nebulae in our galaxy that make headlines, observations like this of objects in our own solar system remind us how much exploration we still have to do locally."

More Hubble images of P/2010 A2 are planned next year, when the asteroid is again in position for observations from Earth.

According to Jewitt, there are still other explanations for the unusual asteroid's appearance. One is the effect of solar radiation, which could increase the body's rate of rotation and spin off mass, forming a tail.

More observations next year could answer the question once and for all.