satellite
Satellite, is a planet around the closed orbit to do the periodic operation of the celestial bodies. Such as the earth's satellite is the moon. However, if the quality of the two celestial bodies, they formed the system is generally called the two-planet system, rather than a planet and a natural satellite. Often, the quality centers of the two celestial bodies are within the planets. Therefore, there are astronomers that Pluto and Ming Wei one should be classified as a double planet, but in 2005 found two new Ming Wei, so that the problem is complicated. ...