Pluto before Charon was discovered. Pluto is more than twice the diameter and a dozen times the mass of the dwarf planet Ceres, the largest object in the asteroid belt. It is less massive than the dwarf planet Eris, a trans-Neptunian object discovered in 2005, though Pluto has a larger diameter of 2376.6 km compared to Eris's approximate diameter of 2326 km. Determinations of Pluto's size had been complicated by its atmosphere, and hydrocarbon haze. In March 2014, Lellouch, de Bergh et al. published findings regarding methane mixing ratios in Pluto's atmosphere consistent with a Plutonian diameter greater than 2360 km,
Dwarf planet has itself been somewhat controversial, as it could imply that these bodies are planets, much as dwarf stars are stars. This is the conception of the Solar System that Stern promoted when he coined the phrase. The older word "planetoid" ("having the form of a planet") has no such connotation, and is also used by astronomers for bodies that fit the IAU definition. Brown states that "planetoid" is "a perfectly good word" that has been used for these bodies for years, and that the use of the term "dwarf planet" for a non-planet is "dumb", but that it was motivated