Eris aka: 2003 UB313

aka 2003 UB313, aka 136199 Eris

The rock that finally got the IAU to adopt a more formal definition of “planet”, which excluded Pluto.

See http://en.wikipedia.org/wiki/Eris_%28dwarf_planet%29

is at least as big as Pluto and about three times farther away from the Sun than Pluto.

The planet was discovered by the Samuel Oschin Telescope at the Palomar Observatory near San Diego, Calif., on Jan. 8, 2005. Image credit: NASA/JPL-Caltech