The eighth planet from the Sun - well, some of the time it's eighth, but more on that later - has a rocky core surrounded by ice, hydrogen, helium and methane. Like the other gas planets, Neptune has rapidly swirling winds, but it is thought to contain a deep ocean of water. Its quick rotation fuels fierce winds and myriad storm systems.

The planet has a faint set of rings and 8 known moons. Because of Pluto's strange orbit, Neptune is sometimes the most distant planet from the Sun.

Since 1979, Neptune was the ninth planet from the Sun. On February 11, 1999, it crossed Pluto's path and once again become the eighth planet from the Sun, where will remain for 228 years.

Neptune was discovered in 1846 after mathematical calculations of Uranus' movements predicted the existence of another large body.