Radar image of Asteroid 2004 BL86 with its small satellite.
The big hunk of rock that zipped by the Earth yesterday morning turns out to have had its own little moon. NASA's Deep Space Network antenna at Goldstone, California took some great radar pictures of the Near-Earth-Orbiting (NEO) asteroids as it made its closest approach to Earth at about 745,000 miles away. That's a little over three times the distance between the Earth and the Moon.
Scientists made good measurements of the asteroid, its moon, and the orbital path around the Sun. The asteroid itself is about 1,100 feet across and the little satellite rock is about 230 feet across. Its current path won't bring it around to us again for a couple hundred years.