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,
Naming of chemical elements planets, dwarf planets, a few asteroids, our star, our planet, and our Moon. Uranium, neptunium, plutonium, cerium, and palladium were named after Uranus, Neptune, Pluto, Ceres, and Pallas respectively, which were at the time of their naming all considered to be planets. (Today, Pluto and Ceres are considered to be dwarf planets, and Pallas is considered to be an asteroid.) The name of the element selenium came from the Greek word for the Moon (Σελήνη, "Selene"). The name helium comes from the Greek word for the Sun (Ἢλιος, "Helios"). This is because the first evidence for helium was in distinctive,