I.

Introduction

Natural Satellite, a body in space that orbits a larger body. The larger body is referred to as the satellite’s primary. Natural satellites that orbit planets are often called moons. Other objects in the solar system that sometimes have satellites include dwarf planets, Kuiper Belt Objects, centaurs, and asteroids. The term satellite is also used to refer to small galaxies that orbit larger galaxies.

Natural satellites are of special interest to astronomers and planetary scientists because these objects provide clues to how the planets and the solar system formed. Studying the orbits of satellites also allows scientists to determine the mass and density of planets and other objects. A number of moons are important to astrobiologists as places where conditions might permit extraterrestrial life to exist. The International Astronomical Union (IAU) gives official names to natural satellites.