Not-quite-a-Planet Xnow dwarf planet Eris

"Since its discovery last year, Eris, which had been known as 2003 UB313, ignited a debate about what constitutes a planet.

"Astronomers were split over how to classify the object because there was no universal definition. Some argued it should be welcomed as the 10th planet since it was larger than Pluto, but others felt Pluto was not a full-fledged planet.

"After much bickering, astronomers last month voted to shrink the solar system to eight planets, downgrading Pluto to a 'dwarf planet,' a category that also includes Eris and the asteroid Ceres...

"Eris, which measures about 70 miles wider than Pluto, is the farthest known object in the solar system at 9 billion miles away from the Sun. It is also the third brightest object located in the Kuiper belt, a disc of icy debris beyond the orbit of Neptune."