Leia: You don't have to do this to impress me.
C-3PO: Sir the possibility of successfully navigating an asteroid field is approximately 3, 720 to 1.
Han: Never tell me the odds.
Narrator: Asteroids collide all the time. At least, we think they do. Close-up views from spacecraft show asteroids to be pockmarked with impact craters. But until recently, astronomers never expected they'd see the recent aftermath of a collision. Now, thanks to Hubble and Swift, they have.
In early 2010, Hubble took a close look at the tail of what astronomers thought was an unusual comet. The curious tail turned out to be wreckage from a collision between two small asteroids. On December 11, 2010, astronomers saw that another asteroid, (596) Scheila, had also grown a tail.
Swifts ability to see ultraviolet light helped astronomers rule out the possibility that they were looking at a comet. None of the gasses characteristic of a comet were detected.
These plumes are clouds of dust, debris from the impact of a smaller asteroid, less than 100 feet across. The shape, evolution, and content of the plumes let astronomers reconstruct what happened. The smaller asteroid would have been heading towards Scheila at about 11,000 miles per hour.
It hit at a low angle with the force of at least a 100 kiloton nuclear bomb. Yet much of the debris fell back onto the asteroid. The particles that escaped were the smallest ones. Easily pushed around by sunlight, this fine dust formed wispy plumes.
When Hubble observed Scheila two weeks later, the plumes were barely visible. Within two months of the outburst, the plumes were completely gone--and with them went any sign from Earth that Scheila even had a collision.
Astronomers estimate that, somewhere in the asteroid belt, events like this may happen as often as every year. Thanks to Hubble and Swift, we're just beginning to see them.