State of an object when its period of rotation is exactly equal to its average The length of time it takes an orbiting object to make one complete trip around its primary body. The Earth’s orbital period around the Sun is 1 year and the Moon's is one 27.3 days. Mercury's orbital period is ~88 days (closest to the Sun) and Neptune's is ~165 years. The Moon is in a synchronous The elliptical path of one body around another, typically the path of a small body around a much larger body. However, depending on the mass distribution of the objects, they may rotate around an empty spot in space • The Moon orbits around the Earth. • The Earth orbits around, and so presents the same face toward Earth at all times.