The Planet Neptune
Basic information and interesting facts about the Planet Neptune. This planet was hypothesised to exist before actually being seen. By observing the motion of Uranus, it was deduced that the gravitational effects of another undiscovered planet must be having unexplained influence on its motion.
Neptune’s largest moon is Triton, but unlike all other large planetary moons in the Solar System, Triton has a retrograde orbit, which means that it was most probably captured rather than forming in place and that it was probably once a dwarf planet in the Kuiper belt.