A mile-wide potentially catastrophic asteroid, complete with its own rotating moon, passed by earth early Sunday morning. The space rocks, called 1999 KW4 by NASA, will be visible until June 7. The larger rock, which is about one mile wide, is shaped like a spinning top, and the smaller rock, about a third of a mile long, is oblong shaped. This is the fourth time this particular asteroid system, which was first spotted in 1999, has passed by earth. It will be some 3.2 million miles away at its closest approach. EarthSky says that North American asteroid hunters may be able to spot the space rocks near the constellation Hydra on May 27.