Neptune is often seen as Uranus' twin planet. It is similar in size and colour, and has a similar chemical make-up. It was discovered in 1846 by Johann Gotfried Galle when he realised that it was difficult to predict Uranus' orbit. It became obvious that there must be something further away in space pulling on Uranus. This object turned out to be Neptune.
The
giant blue planet, slightly smaller than Uranus at 49,500 kilometres wide
(Uranus is 52,000 kilometres wide) takes 165 years to orbit the Sun, meaning that it never
completes a complete journey around the Sun during the lifetime of
anybody on Earth. The Earth, which is surprisingly the
next biggest planet in the Solar System, could fit into Neptune 60
times!
Voyager 2, a space craft designed to visit the four Gas
Giants (Jupiter, Saturn, Uranus and Neptune) arrived at Uranus in 1986, and revealed a
bland, boring world. Scientists expected Neptune to be the same.
However, pictures from Voyager, when it arrived at
Neptune on 24th August 1989, (12 years after the Voyager probes were launched)
showed Neptune to be a deep blue-coloured planet with white,
whispy clouds in its atmosphere, the strongest
winds in the Solar System, and a dark
spot,
similar to Jupiter's Great Red Spot, which was the size of Earth. Incomplete rings, looking
like arcs, orbited the planet, suggesting that they haven't had
time to completely form yet, and one of Neptune's moons (Triton) showed that, with its
eruptions of nitrogen gas, even at the furthest reaches of the Solar
System,
geological activity still takes place.
Neptune, like Jupiter, Saturn and Uranus, has a thick gassy atmosphere full of mainly hydrogen and helium. Below this are huge amounts of rock (not solid though), water and liquid ammonia. The planet also contains Methane which gives the planet a blue colour, like Uranus. Winds on Neptune can blow at speeds up to 2,000 kilometres an hour!
Surrounding Neptune are eight moons (discovered so far). These moons are all very small, apart from Triton, an active moon. For more details, click here.
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