A natural satellite, more commonly referred to as a moon, is an astronomical body that orbits a planet or a 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. As of October 2016, there are over 300 minor planets known to have moons.