Natural satellite achieved hydrostatic equilibrium, and Uranus has five. It has been suggested that some satellites may potentially harbour life. Among the identified dwarf planets, Ceres has no known natural satellites. Pluto has the relatively large natural satellite Charon and four smaller natural satellites; Styx, Nix, Kerberos, and Hydra. Haumea has two natural satellites, and Eris and Makemake have one each. The Pluto–Charon system is unusual in that the center of mass lies in open space between the two, a characteristic sometimes associated with a double-planet system. The seven largest natural satellites in the Solar System (those bigger than 2,500 km across)
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,