Neptune

Neptune  though slightly smaller than Uranus, is more massive and therefore more dense. It radiates more internal heat, but not as much as Jupiter or Saturn.Neptune has thirteen known satellites. The largest, Triton, is geologically active, with geysers of liquid nitrogen.Triton is the only large satellite with a retrograde orbit. Neptune is accompanied in its orbit by a number of minor planets, termed Neptune Trojans, that are in 1:1 resonance with it.