Double planet frequently been described by many scientists as "double dwarf planets" ("double planets" prior to the 2006 definition of "planet"). The International Astronomical Union (IAU) currently calls Charon a satellite of Pluto, but has explicitly expressed a willingness to reconsider the bodies double dwarf planets at a future time. The Moon-to-Earth mass ratio of 0.01230 (≈ ) is also notably close to 1 when compared to all other satellite-to-planet ratios. Consequently, some scientists view the Earth-Moon system as a double planet as well, though this is a minority view. Eris's lone satellite, Dysnomia, has a radius somewhere around that of Eris;
Pluto define the term "planet" formally in 2006, during their 26th General Assembly. That definition excluded Pluto and reclassified it as a dwarf planet. Pluto is the largest and second-most-massive known dwarf planet in the Solar System, and the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but is less massive than Eris. Like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—about one-sixth the mass of the Moon and one-third its volume. It has a moderately eccentric and inclined orbit during which it