Largest retrograde satellite
Triton, the largest satellite of Neptune, measures 2,706 km (1,681 miles) across. It is the seventh largest moon in the Solar System, and the largest moon which orbits its planet backwards. Its retrograde orbit means Triton is slowly losing energy and spiralling in towards Neptune. Between 10 and 100 million years from now Triton will be so close to Neptune that it will be ripped apart by tidal forces, forming a new ring system around the planet