The number of dwarf planets even among known objects is not certain. In 2019, Grundy et al. argued based on the low densities of some mid-sized trans-Neptunian objects that the limiting size required for a trans-Neptunian object to reach equilibrium was in fact much larger than it is for the icy moons of the giant planets, being about 900–1000 km diameter. There is general consensus on Ceres in the asteroid belt and on the eight trans-Neptunians that probably cross this threshold— Orcus, Pluto, Haumea, Quaoar, Makemake, Gonggong, Eris, and Sedna.