Claims of the existence of other moons of Earth—that is, of one or more natural satellites other than the Moon that orbit Earth—have existed for some time. Several candidates have been proposed, but none has been confirmed. The 19th and 20th centuries have seen genuine scientific searches for more moons, but the possibility has also been the subject of a number of dubious non-scientific speculations as well as a number of likely hoaxes.
Although the Moon is Earth’s only natural satellite, there are a number of near-Earth objects (NEOs) with orbits that are in resonance with Earth. These have been called, inaccurately but provocatively, “second”, “third” or “other” moons of Earth. NEOs include quasi-satellites that orbit the Sun in resonance with Earth, which appear to orbit a point other than Earth itself, such as the orbital path of the NEO asteroid 3753 Cruithne. Earth trojans, such as 2010 TK7, are NEOs that orbit the Sun (not the Earth) on the same orbital path as Earth, appear to lead or follow Earth along the same orbital path.
Other small natural objects in orbit around the Sun may fall temporarily into orbit around Earth. This would make them natural satellites of Earth, but only temporarily. To date, the only confirmed example has been 2006 RH120 in Earth orbit during 2006 and 2007, though further instances are already predicted. Source: Claimed moons of Earth