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Engine Sound

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Engine

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Leia: You don't have to do this to impress me. C-3PO: Sir the

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asteroid field is approximately 3, 720 to 1. Han: Never tell me the odds.

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Narrator: Asteroids collide all the time.

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At least, we think they do. Close-up views from spacecraft show asteroids

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to be pockmarked with impact craters. But until recently, astronomers

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never expected they'd see the recent aftermath of a collision.

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Now, thanks to Hubble and Swift, they have. In

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early 2010, Hubble took a close look at the tail of what astronomers thought was an unusual

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comet. The curious tail turned out to be wreckage from a collision between two

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small asteroids. On December 11, 2010,

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astronomers saw that another asteroid, (596) Scheila, had also grown a tail.

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Swifts ability to see ultraviolet light helped astronomers rule

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out the possibility that they were looking at a comet. None of the gasses characteristic

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of a comet were detected. These plumes are clouds of dust,

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debris from the impact of a smaller asteroid, less than 100 feet across.

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The shape, evolution, and content of the plumes let astronomers reconstruct

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what happened.

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The smaller asteroid would have been heading towards Scheila at about 11,000 miles per

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hour.

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Music

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It hit at a low angle with the force of at least a 100 kiloton nuclear

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bomb. Yet much of the debris fell back onto the asteroid.

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The particles that escaped were the smallest ones. Easily

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pushed around by sunlight, this fine dust formed wispy plumes.

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When Hubble observed Scheila two weeks later, the

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plumes were barely visible. Within two months of the outburst,

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the plumes were completely gone--and with them went any sign from Earth that Scheila even had

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a collision. Astronomers estimate that, somewhere in the asteroid

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belt, events like this may happen as often as every year. Thanks to Hubble and