Luna, also known as the Moon, is the only natural satellite of the Earth and the fifth largest moon in the Sol System. It is the largest natural satellite of a planet in the Sol System relative to the size of its primary, having 27% the diameter and 60% the density of Earth, resulting in 1⁄81 its mass. Among satellites with known densities, the Moon is the second densest, after Io, a satellite of Jupiter.
Starting in the early Shadow War, the Moon was colonized as a means to pre-emptively avoid overpopulating Earth.