X-Shaped Space Thing Is Smashed-Up Asteroid
* By Dave Mosher Email Author
* October 13, 2010 |
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.”
October 14, 2010 6:33 PM
Aftermath of Asteroid Collision Caught on Camera
Somewhere between the orbits of Mars and Jupiter, a peculiar object with the even more peculiar-sounding name of P/2010 A2 was recently observed cruising through an asteroid belt in a way that astronomers found, well, peculiar.
Hubble Image of P/2010 A2
(Credit: NASA, ESA, and D. Jewitt (UCLA))
Judging from the debris in its tail, P/2010 A2 was thought at first to be a comet. But astronomers studying the object through the Hubble Space Telescope subsequently changed their minds, suggesting that what they'd been looking at was an asteroid. The asteroid with a comet-like tail explanation has now been reinforced by the European Space Agency's Rosetta spacecraft. UCLA astronomer David Jewitt, who authored one of the two papers on the topic noted in an interview with Nature News the rarity of the event, adding that this marked the first time that astronomers have actually observed an asteroid being disrupted.
The finding was particularly excited to scientists searching for evidence that would shed more light on the origins of dust found in the solar system. The thinking is that the asteroid got diverted from its usual orbit sometime early in 2009.
"I knew that this was an object the likes of which we hadn't seen before," he said.
The researchers led by Jewitt posit that the tail might have resulted from a collision with a smaller asteroid. (A competing explanation suggests it might be due to solar radiation.) A second paper on the debris trail lines up behind the asteroid collision scenario.