Lunar orbit Lunar orbit In astronomy, lunar orbit (also known as a selenocentric orbit) is the orbit of an object around the Moon. As used in the space program, this refers not to the orbit of the Moon about the Earth, but to orbits by various manned or unmanned spacecraft around the Moon. The altitude at apoapsis (point farthest from the surface) for a lunar orbit is known as apolune, apocynthion, or aposelene, while the periapsis (point closest to the surface) is known as perilune, pericynthion, or periselene, from names or epithets of the moon goddess. Low lunar orbit (LLO)—orbits below altitude—are
Earth that it formed from the collision of a Mars-size protoplanet called Theia with the early Earth. This hypothesis explains (among other things) the Moon's relative lack of iron and volatile elements and the fact that its composition is nearly identical to that of Earth's crust. Earth has at least five co-orbital asteroids, including 3753 Cruithne and . A trojan asteroid companion, , is librating around the leading Lagrange triangular point, L4, in the Earth's orbit around the Sun. The tiny near-Earth asteroid makes close approaches to the Earth–Moon system roughly every twenty years. During these approaches, it can orbit Earth