Asteroid's moon seen during Earth flyby

The asteroid that flew close to Earth Monday didn't come alone. NASA images released Monday reveal the asteroid, officially known as 2004 BL86, has its own small moon. The grainy, black and white photos show the asteroid, about a third of a mile in size, spinning through space, with its 230-foot-wide moon trailing behind.

It was far enough that it didn't pose a threat to Earth, but close enough to give scientists and amateurs a chance to observe a large asteroid up close. Observers on the ground didn't see much when the asteroid was closest to Earth Monday morning, because it wasn't at its brightest. Only a portion of its illuminated side was visible, according to Sky & Telescope magazine. The asteroid brightened as it got farther from the Earth because its face became more fully illuminated, the magazine said.

"While it poses no threat to Earth for the foreseeable future, it's a relatively close approach by a relatively large asteroid, so it provides us a unique opportunity to observe and learn more," Don Yeomans, the recently retired manager of NASA's Near Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California, said in a NASA news release.

Observers without binoculars or a scope watched from their computers on The Virtual Telescope Project 2.0. The asteroid was discovered on January 30, 2004, by a telescope of the Lincoln Near-Earth Asteroid Research survey in White Sands, New Mexico.

CNN.com story