Fictional planets of the Solar System while yet others are purely fictional and were never intended as serious hypotheses about the structure of the Solar System. Vulcan was a hypothetical planet supposed to revolve around the Sun inside the orbit of Mercury, invoked to explain certain irregularities in Mercury's orbit. The planet was proposed as a hypothesis in 1859, and abandoned not later than 1915. The name "Vulcan" has been used for various other fictional planets, in and out of the Solar System, that do not correspond to the hypothetical planet Vulcan. The planet Vulcan in the "Star Trek" franchise, for instance, is specified as orbiting
Satellite system (astronomy) the largest satellite system, the Jovian system, with 79 known moons (including the large Galilean moons) and the Saturnian System with 62 known moons (and the most visible ring system in the Solar System). Both satellite systems are large and diverse. In fact all of the giant planets of the Solar System possess large satellite systems as well as planetary rings, and it is inferred that this is a general pattern. Several objects farther from the Sun also have satellite systems consisting of multiple moons, including the complex Plutonian system where multiple objects orbit a common center of mass, as