Eris, the dwarf planet whose orbit is beyond Neptune's orbit, has one small moon named Dysnomia. The dwarf planet was first spotted in 2003 and confirmed in 2005.
As a dwarf planet, Eris orbits the sun but is not the dominant gravitational force in its orbit. However, a dwarf planet can have one or more moons, as seen with both Eris and Pluto. The existence of moons on far off planets such as Eris is important for measuring the size of the orbited planet. Dysnomia derives its name from the same Greek myths as Eris. In Greek mythology, Dysnomia is the daughter of Eris.