Asteroid cruises past Earth ... with a partner!

A good-sized asteroid sailing past our planet right now turns out to be two giant rocks doing a celestial jig. The setup, catalogued as 2008 BT18, was thought to be nearly a half-mile wide after its discovery by MIT's LINEAR search program in January. Nothing else was known about it. Now seen as two objects orbiting each other, the pair will be closest to Earth on today, at about 1.4 million miles (2 million kilometers) away. That's nearly six times as far from us as the moon.