Neptune is the outermost planet of the solar system. It is slightly smaller than Uranus. Neptune has also been visited by only one spacecraft, Voyager 2, on Aug 25 1989.
Neptune has a mark on it that looks very similar to Jupiter's great spot. Just like Jupiter, this is caused by violent storms.
The weather is very extreme on Neptune - the wind on Neptune is the strongest on any planet, and blows at 1,300 miles per hour - as fast as a jet fighter plane.
Neptune is 4,500,000,000 km away from the sun.
