Scientific American is reporting on the first-ever discovery of an asteroid with two moons. Double-asteroid systems (one orbits the other) have been known for some time, and more complex arrangements have been predicted but not seen until now. Why doesn't this make it a planet? Well, by using the orbits of the "moons", scientists have determined the main asteroid is only a bit more dense than water. In other words, it's probably just a conglomeration of smaller rocks instead of a single solid body.