Moons of Pluto moons orbit Pluto at two to four times the distance of Charon, ranging from Styx at 42,700 kilometres to Hydra at 64,800 kilometres from the barycenter of the system. They have nearly circular prograde orbits in the same orbital plane as Charon. All are much smaller than Charon. Nix and Hydra, the two larger, are roughly 42 and 55 kilometers on their longest axis respectively, and Styx and Kerberos are 7 and 12 kilometers respectively. All four are irregularly shaped. The Pluto system is highly compact and largely empty. Moons could potentially orbit Pluto at up to 53% (or 69%,
Eris (dwarf planet) object was classified as a dwarf planet, because there is already an asteroid with that name, 399 Persephone. With the dispute resolved, the discovery team proposed "Eris" on September 6, 2006. On September 13, 2006 this name was accepted as the official name by the IAU. Brown decided that, because the object had been considered a planet for so long, it deserved a name from Greek or Roman mythology, like the other planets. The asteroids had taken the vast majority of Graeco-Roman names. "Eris", whom Brown described as his favorite goddess, had fortunately escaped inclusion. The name in part reflects