A relatively small body orbiting a larger one that in turn orbits a star. In the solar system, all of the planets except Mercury and Venus have satellites. Well over 100 planetary satellites are known to exist, of which a total of 101 were definitely established by March 1, 2004, distributed as follows: Earth, 1; Mars, 2; Jupiter, 38; Saturn, 30; Uranus, 21; Neptune, 8; and Pluto, 1. Additional satellites have been observed in all four giant systems (Jupiter, Saturn, Uranus, and Neptune); more observations are needed to define their orbits. The close flyby of the Galileo spacecraft (enroute to Jupiter) of the asteroid 243 Ida in 1993 revealed the presence of a 0.9-mi-diameter (1.5-km) satellite, now known as Dactyl. This unexpected discovery has been followed by the detection of several other asteroid satellites by Earth-based observers. Several Kuiper Belt objects (distant comet nuclei) have also been observed to be binaries.