On the 14th of September, 2006, Eris became the official name of the object previously known officially as 2003 UB313, and by its nickname Xena. Eris had caused controversy in astronomical circles because it was the first Trans-Neptunian Object (TNO) found to be bigger than Pluto, and would either have to be a planet itself, or Pluto would have to be demoted. (Trans-Neptunian objects are objects whose orbit lies beyond that of Neptune.) In the event, on 24th August, 2006, the International Astronomical Union (IAU) decided to create a new category of dwarf planets, and Pluto was demoted to this new category. This discord made the name "too perfect to resist" to its discoverer, Mark Brown, and is sure to meet widespread approval among Discordians everywhere, because of its association with the goddess of discord. The dwarf planet's moon has also been named as Dysnomia, the daughter of Eris, representing lawlessness. Lucy Lawless also played Xena in the TV series Xena, Warrior Princess.

Eris was originally first seen in October 2003, although its importance was not realised until 2005, when Brown and his team at the California Institute of Technology reanalysed the 2003 data using wider parameters. The Hubble Space Telescope measured Eris' diameter to be approximately 2400km, making it slightly larger than Pluto. Eris orbits the Sun in 556.7 years, with an aphelion distance of 97.56 AU (Astronomical Units), when it will be at its furthest distance from the Sun. Its perihelion, however, when it will be closest to the Sun, is only 37.8 AU.