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Triple Asteroid Spotted in "Near-Earth" Space

Triple Asteroid System (Yes, That Means Mini-Moons) Spotted Near Earth
By John Borland February 14, 2008

Researchers using the massive Arecibo telescope in Puerto Rico have discovered the first observed example of a triple asteroid – a center body, orbited by two smaller ones – in near-Earth space.

It's possible this is going to spawn a whole new LOLasteroid genre. But in fact, there are serious scientific issues at stake here.
Triple asteroid systems aren't uncommon in the belt between Mars and Jupiter, but this is the first one noted relatively near Earth, where the actual shapes of the objects can be seen.
Researchers say the central body is a rock about 1.5 miles in diameter. The larger of the "moons" is about half that size, and the smallest just 1000 feet across.
"This discovery has extremely important implications for ideas about the origins of near-Earth asteroids and the processes responsible for their physical properties," said (Cornell University astronomer Michael) Nolan. "Double, or binary, asteroid systems are known to be fairly common - about one in six near-Earth asteroids is a binary - but this is the first near-Earth triple system to be discovered."

The triple-rock system should provide insight into how near-Earth asteroid systems evolve over time, and whether multiple-asteroid formations can form nearby, or were collected together in the main asteroid belt, the researchers say.
The asteroid system, known as 2001 SN263, was viewed by Arecibo on Feb. 11, when it was about 7 million miles from Earth.
First near-Earth triple asteroid discovered by Arecibo Observatory astronomers - a mere 7 million miles from Earth [Cornell press release]