Pluto is now King of the distant dwarf planets, but are there other larger planets out there?
The six most distant known objects in the solar system with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Moreover, when viewed in three-dimensions, they are all tilted nearly identically away from the plane of the solar system. Such an orbital alignment can only be maintained by some outside force. In a new paper, Batygin and Brown show that a planet with 10 times the mass of the earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration.