X Marks the Spot of a Dramatic Asteroid Collision

By Jennifer Welsh | October 14, 2010 11:18 am

asteroid mashup

Out in the asteroid belt beyond Mars, two asteroids rendezvous-ed in the darkness, with explosive results. Atomic bomb level explosive.

These two asteroids, one probably 400 feet wide and the other, smaller asteroid around 10 to 15 feet across, collided sometime in early 2009. This is the first time we humans have observed an asteroid impact right after it has occurred, and the first time a resulting x-shape has been seen. Researchers aren’t sure what caused the novel shape, and they were surprised by how long the dust tail has lasted. The analysis of the finding, originally announced earlier this year, is published in Nature this week.

From Phil Plait, DISCOVER’s Bad Astronomer:

This is a false-color image showing the object, called P/2010 A2, in visible light. The long tail of debris is obvious; this is probably dust being blown back by the solar wind, similar to the way a comet’s tail is blown back. What apparently has happened is that two small, previously-undiscovered asteroids collided, impacting with a speed of at least 5 km/sec (and possibly faster). The energy in such a collision is like setting off a nuclear bomb, or actually many nuclear bombs! The asteroids shattered, and much of the debris expanded outward as pulverized dust.

Looking at the image, the bright spot to the left is most likely what’s left of one of the two asteroids, a chunk of rock estimated to be a mere 140 meters (450 feet) across. In the press release they’re not clear about the curved line emanating to the right of the nucleus. It may be — and I’m spitballing here — dust blown back from a stream of chunks, since the tail is broad and appears to originate from that swept curve, and not from the nucleus itself. The other filament perpendicular to the curve is from yet another piece of debris.

Read the rest of his original post, which includes more information about why we should pay more attention to asteroids. Since the first spotting, researchers have been tracking the collision site with the help of the Hubble Space Telescope, watching what happens over time.

“We expected the debris field to expand dramatically, like shrapnel flying from a hand grenade,” said astronomer David Jewitt of the University of California in Los Angeles, who is a leader of the Hubble observations. “But what happened was quite the opposite. We found that the object is expanding very, very slowly.” [NASA Press release]

These collisions give rise to a cloud of dust (which also forms the tail coming off of the collision site). Looking at the amount of dust created by this interaction caused Jewitt to re-think some assumptions about the origins of the solar system’s dust.

“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. “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. Knowing how the dust was produced will yield clues about those invisible bodies.” [NASA Press release]

Related content:
80beats: Found: One of Neptune’s Asteroid Stalkers
80beats: Satellites Collide Over Siberia, Creating Showers of Space Debris
80beats: Was Mars’ Moon Phobos Born From a Violent Collision?
Bad Astronomy: Video of asteroid near miss from this morning
Bad Astronomy: Hubble spins an asteroid
Bad Astronomy: When worlds really do collide!
Cosmic Variance: Space Junk 1: Science 0

Image: NASA, ESA, and D. Jewitt (UCLA)

  • Alex

    – Cdn and American astronauts want world to start getting ready for asteroids… VIDEO: Our terrifyingly crowded solar system…CBS News: Jupiter Hit by Large Object, NASA Says…Californian Congressman for Planet X Forsight – The Sky is Falling…Stephen Hawking: “Asteroid Impacts Biggest Threat to Intelligent Life in the Galaxy…Giant propeller structures seen in Saturn’s rings…NASA: Sun’s Nemesis Pelted Earth with Comets, Study Suggests:

  • Alsid

    If the original asteroids were 400 feet, and 10-15 feet. How is the one in the image 450 feet across? I’m not a physicist, but in an atomic level explosion I wouldn’t expect the asteroid to grow….

  • Jennifer Welsh


    Sorry for the confusion, the estimates for the size of the larger asteroid are not certain, and when Phil wrote his post earlier in the year they were even less certain.

    NASA’s current estimate is: “The 400-foot-wide object in the Hubble image is the remnant of a slightly larger precursor body. Astronomers think a smaller rock, perhaps 10 to 15 feet wide, slammed into the larger one.” (http://hubblesite.org/newscenter/archive/releases/2010/34/text/)

    Since we don’t really have a clear estimate of how large the original asteroid was, I went with the 400 foot spec from NASA.

    Thanks for reading and commenting! Sorry for the confusion.


  • YouRang

    It seems pretty clear the smaller object is at the cross of the x and that both objects are shedding medium size stuff which is shedding dust. Oops not medium size (that implies bigger than the smaller asteroid). I meant moderate size stuff–bigger than dust and smaller than the asteroids inch to a meter.

  • Messier Tidy Upper

    Nice article. Thanks. :-)

    Saw this on tonights SBS news (Aussie TV) as well.

  • A. Reader

    Two asteroids – in the darkness of space!
    How frightening! How romantic!

    I just thank God that I live on a planet that receives light from the Sun. How horrible it must be drifting endlessly in the horrible “darkness of space”!



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