Planetary satellite systems

The Moon is the only natural satellite of Earth. It orbits around Earth at an average distance of , a distance roughly 30 times the width of Earth. It completes an orbit (lunar month) in relation to Earth and the Sun (synodically) every 29.5 days. The Moon and Earth are bound by gravitational attraction, which is stronger on the sides facing each other. The resulting tidal forces are the main driver of Earth's tides, and have pulled the Moon to always face Earth with the same near side. This tidal locking effectively synchronizes the Moon's rotation period (lunar day) to its orbital period (lu

thumb|right|Artist's impression of candidate exomoon Kepler-1625b I orbiting its planet.

hypothetical natural satellite of Venus

designation of an astronomical body after its discovery and before its official name

claims that Earth may have other natural satellites

supposed natural satellite orbiting Mercury

proportionality of orbital periods for two celestial bodies