Jupiter
Jupiter or Sol V is the fifth planet from Sol (not including the Fifth Planet). As gas giant, Jupiter has immense gravity. The planet has many moons including, in the future, Voga.
In Revenge of the Cybermen, upon hearing of Voga's existence, the Doctor states that Jupiter now has thirteen moons, as only twelve moons were known at the time the script was written. Since then at least another 50 have been discovered. Stephen Cole's novel "To the Slaughter" addresses this issue by giving the Solar System a "spring clean" which includes removing most of Jupiter's moons and leaving the largest 12. Voga would have entered Jupiter's orbit after this happened.
In The Android Invasion Guy Crayford claimed that his spaceship had been trapped in orbit around Jupiter.
External Links
There are numerous websites about Jupiter. Two which make good starting points are
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter
http://www.nineplanets.org/jupiter.html
