Astronomers are now almost certain an x-shaped object discovered in the asteroid belt earlier this year is the first documented asteroid-to-asteroid collision.
There’s a small chance a space rock may have instead spun itself into pieces, but two independent teams of scientists think it’s a matter of time before that explanation is snuffed out. Whatever happened to create the trail, it’s a big clue to what’s littering the solar system with fine particles.
“This is the first time we’ve seen anything like this,” said David Jewitt, an astronomer at the University of California Los Angeles and author of one of two studies of the object, P/2010 A2, published Oct. 13 in the journal Nature. “It’s a door-opener to the study of disintegrating asteroids.”
Jewitt, who used new Hubble Space Telescope images to chart P/2010 A2’s progress from January through May, said asteroid belt objects die either by colliding with one another or by rotating so quickly they fly apart.
“What we don’t know is which is more frequent or important,” Jewitt said, adding that such smash-ups contribute to a persistent cloud of dust in the solar system known as the Zodiacal cloud.
The U.S. Air Force’s near-Earth asteroid program discovered the dust trail on January 6 and reported it as a comet. But astronomers later determined the 30,000-mile-long trail is made of rocky dust, signaling the remains of an asteroid. If a collision did spew out the dust, Jewitt said a small asteroid traveling more than 3 miles per second careened into a 75-mile-wide asteroid, blasting off 100,000 tons of rocky dust.
“The energy would have been comparable to a small atomic bomb, maybe a kiloton of TNT,” he said.
Despite the finding, Jewitt thinks such events are less likely than previously thought to contribute to the Zodiacal cloud of dust littering the solar system.
“The dust just doesn’t come from asteroids, it comes from comets,” he said, noting that P/2010 A2’s cloud expanded more slowly than anyone expected. “Our best guess now is that comets are the bigger source.”
Colin Snodgrass, an astronomer at the Max-Planck Institute for Solar System Research in Germany who worked with a different team of scientists, agrees.
“It’s about 1,000 to 10,000 times less than what you would expect if asteroid collisions were the major contributors,” Snodgrass said.
Snodgrass said big new telescopes, such as the Large Synoptic Survey Telescope, should pick more asteroid collisions out of the sky in the coming years.
“This size we’ll see every 1 to 10 years,” he said, referring to P/2010 A2. “The smaller collisions are more common, so we’ll see those once a year, maybe every month or so.”
Video: NASA, ESA and D. Jewitt. Images: 1) NASA, ESA and D. Jewitt, 2) Colin Snodgrass.
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