Dysnomia[1] is the only known moon of the dwarf planetEris. It was found on September 10, 2005 by Michael E. Brown and his team at the W. M. Keck Observatory.[2] It is probably about 600 km in diameter (across),[2] although it may be up to 800 km in diameter.[2] The moon was named Dysnomia[3] (from the Ancient Greek word Δυσνομία that means "lawlessness") after the daughter of the Greek goddess Eris.[4]