English: Asteroid 2008 BT18 is gliding past Earth this weekend and astronomers have just discovered that it is a binary system. "The sizes of the two components are 600 m for the primary and >200 m for the secondary," says Lance Benner of JPL. "The primary looks spheroidal, but we don't yet know about the shape of the secondary." Benner and others using a giant radar in Arecibo, Puerto Rico, obtained this "delay-doppler" image of the pair on July 7th.