Small moon discovered orbiting a near Earth asteroid

NASA astronomers studying a speeding asteroid which passed close to our planet on Monday learned it carries an orbiting moon of its own around the icy rock as it moves across our solar system.

In newly released radar images from the space agency, asteroid 2004 BL86 can be seen spinning while its unnamed moon moves closer frame by frame. The space duo flew past Earth on Monday morning (EST) from a distance of 745,000 miles or three times the distance from the Earth to our moon.

"(The) flyby was the closest approach the asteroid will make to Earth for at least the next two centuries," DC Agle, spokesperson at NASA Jet Propulsion Laboratory, said on Monday. "It is also the closest a known asteroid this size will come to Earth until asteroid 1999 AN10 flies past our planet in 2027."

NASA Near Earth Objects program cooperates with universities and the private sector in studying and discovering asteroids using high gain radar antennas across the globe. "Radar is a powerful technique for studying an asteroid's size, shape, rotation state, surface features and surface roughness, and for improving the calculation of asteroid orbits. Radar measurements of asteroid distances and velocities often enable computation of asteroid orbits much further into the future than if radar observations weren't available."

"In the near-Earth population, about 16 percent of asteroids that are about 655 feet or larger are a binary or even triple systems," Agle added. The 1100-foot near-Earth asteroid was discovered in January 2004 by astronomers at White Sands, N.M.