The dwarf planet 2003 UB313, which had been nicknamed 'Xena,' has been given the formal name of Eris, the International Astronomical Union announced on 13 September. Eris, which was discovered in January 2005, was named for the Greek goddess of discord. Its moon has been named Dysnomia, for the daughter of Eris, the demon goddess of lawlessness. Eris was assigned dwarf planet status in an IAU resolution approved in August (see Eos 87(35), 2006) along with Pluto and Ceres. Pluto's demotion prompted the Minor Planet Center, which operates under the auspices of the IAU, to assign Pluto an asteroid number, 134340, on 7 September.