Neil deGrasse Tyson may get the blame, but it was Caltech astronomer Mike Brown who really killed Pluto, and now he and his colleague Konstantin Batygin want everyone to change their planet count again because they've claimed to discover a Neptune-sized object floating way, way, way out in the dark. "Planet IX," as many have dubbed it, has not been seen yet—which will be tough since it is thought to be very distant, very slow, and very cold. The evidence for its existence however, is quite strong, and is similar to the way Neptune was discovered in the first place.

Sources: Ars Technica | Science