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 recognized five bodies as dwarf planets since 2008: Ceres, Pluto, Eris, Haumea, and Makemake. Ceres and Pluto are known to be dwarf planets through direct observation. Eris is recognized as a dwarf planet because it is more massive than Pluto (measurements by "New Horizons" indicate that Pluto's diameter is larger than that of Eris), whereas Haumea and Makemake qualify based on their absolute magnitudes. In relative distance from the Sun, the five are: Mike Brown considers an additional six trans-Neptunian objects to be "nearly certainly" dwarf planets with diameters at or above 900 kilometers. These objects are: Tancredi et al.