The Moon is the object that is closest to the Earth in all three systems - the Earth-Moon system, the Solar System and the Local Group. In the Earth-Moon system, the Moon is the only other celestial body that is in orbit around the Earth. In the Solar System, the Earth-Moon system is the closest to the Sun, although there are other planets that are closer to the Sun than Earth is. In the Local Group, the Earth-Moon system is part of the Milky Way galaxy, which is the largest galaxy in the group, but it is not necessarily the closest to the center of the group.