Charon (moon) but they are not large enough to be spherical, and they are simply considered to be satellites of Pluto (or of Pluto–Charon). Charon (moon) Charon, also known as (134340) Pluto I, is the largest of the five known natural satellites of the dwarf planet Pluto. It has a mean radius of 606 km. It was discovered in 1978 at the United States Naval Observatory in Washington, D.C., using photographic plates taken at the United States Naval Observatory Flagstaff Station (NOFS). With half the diameter and one eighth the mass of Pluto, Charon is a very large moon in comparison to
Natural satellite Natural satellite A natural satellite or moon is, in the most common usage, an astronomical body that orbits a planet or minor planet (or sometimes another small Solar System body). In the Solar System there are six planetary satellite systems containing 185 known natural satellites. Four IAU-listed dwarf planets are also known to have natural satellites: Pluto, Haumea, Makemake, and Eris. , there are 334 other minor planets known to have moons. The Earth–Moon system is unique in that the ratio of the mass of the Moon to the mass of Earth is much greater than that of any other