Moons of Pluto while searching for Plutonian rings. Styx, announced on 7 July 2012, was discovered while looking for potential hazards for "New Horizons". Charon is about half the diameter of Pluto and is so massive (nearly one eighth of the mass of Pluto) that the system's barycenter lies between them, approximately 960 km above Pluto's surface. Charon and Pluto are also tidally locked, so that they always present the same face toward each other. The IAU General Assembly in August 2006 considered a proposal that Pluto and Charon be reclassified as a double planet, but the proposal was abandoned. Pluto's four small
Eris (dwarf planet) retains an oblique reference to Eris's old informal name "Xena", portrayed on TV by Lucy Lawless. In the 2010s, on the heels of the successful Pluto flyby there were multiple studies for follow-on missions to explore the Kuiper belt, and Eris was evaluated among the candidates. It was calculated that a flyby mission to Eris could take 24.66 years using a Jupiter gravity assist, based on launch dates of 3 April 2032 or 7 April 2044. Eris would be 92.03 or 90.19 AU from the Sun when the spacecraft arrives. Eris (dwarf planet) Eris (minor-planet designation 136199 Eris) is the