Eris (dwarf planet) Edit
See also Planet X.
Eris (minor-planet designation 136199 Eris) Edit
The most massive and second-largest dwarf planet known in the Solar System. It is also the ninth-most-massive known body directly orbiting the Sun,[g] and the largest known body in the Solar System not visited by a spacecraft. It is measured to be 2,326 ± 12 kilometers (1,445.3 ± 7.5 mi) in diameter. Eris is 27% more massive than dwarf planet Pluto, though Pluto is slightly larger by volume. Eris's mass is about 0.27% of the Earth's mass.
the discovery team proposed Eris on September 6, 2006. On September 13, 2006 this name was accepted as the official name by the IAU. Brown decided that, because the object had been considered a planet for so long, it deserved a name from Greek or Roman mythology, like the other planets. The asteroids had taken the vast majority of Graeco-Roman names. Eris Discordia, whom Brown described as his favorite goddess. The name in part reflects the discord in the astronomical community caused by the debate over the object's (and Pluto's) classification.
Some SubGenii and Discordians claim Eris is the same world as Planet X.