This animation shows the orbits of the commonly known solar system bodies and includes the orbits of Pluto in white and the recently announced "10th planet", Eris (2003 UB313), in red. The light blue orbit belongs to Sedna which is currently the record holder for the most distant solar system object.
Eris made such a fuss because it is larger than Pluto – 27% more massive. Some people labeled it as the tenth planet while others did not think it should join the ranks of the nine planets we had. Finally, the International Astronomical Union (IAU) met to decide on a definition of a planet. Eventually, they decided on a definition in 2006, and 2003ub313 was not classified as a planet but rather a dwarf planet.
Read more: http://www.universetoday.com/43307/2003-ub313/#ixzz2jXxIyqpz