There’s something odd floating around in the outer solar system. Actually, there’s lots of odd things floating around in the outer solar system, but 2002 UX25 is one of the most baffling.
The mid-sized Kuiper belt object (KBO) measures 650 kilometers (400 miles) across, and yet it has a density less than water (less than 1 gram per cubic centimeter). Yes, if you put it in a huge bathtub, 2002 UX25 would float.
As we probably all know by now, the Kuiper belt — a populated region of the solar system found just beyond the orbit of Neptune — is a strange place. Once thought to have a population of just one, astronomers have identified thousands of other minor planetary bodies. In fact, it was the accelerated discoveries in the Kuiper belt that ultimately led to the reclassification (or demotion, depending on which way you look at it) of Pluto from “planet” to lowly “dwarf planet.”