Model of the internal structure of the planet Neptune. Neptune is the most distant planet from the Sun, orbiting at just over 30 times the Earth_Sun distance. It is some 49,500 kilometres in diameter, just under four times Earth磗 diameter. It has a thin ring system. The tops of its clouds show weather patterns similar to Jupiter, with streaks of cloud, huge storm systems and the fastest winds in the Solar System. Beneath these clouds is a thick atmosphere of hydrogen, helium and methane light green. Below that is a thick layer of 磇ces?dark green, largely water, ammonia and methane that exist as a hot, dense liquid. At its centre is a rocky core grey, formed of iron, nickel and silicates. Neptune磗 blue colour comes from traces of methane, which absorbs red light.