The Solar System

Neptune

When Neptune was discovered in 1846 astronomers thought it was a star. It is the eighth planet from the sun. It does not shine so brightly, so it is only visible when you use a telescope. It appears as a green - bluish disc, like Uranus.

It takes Neptune, which is almost 4.5 billion km away from Earth, almost 165 years to travel around the sun once . Neptune's day is shorter than an Earth day - only 16 hours.

Neptune has a few dark spots. Scientists think that these spots are tremendous hurricanes that travel across the frozen planet. Strong and icy winds of up to 1000 km an hour blow on this planet. They are the fastest winds ever measured in our solar system. Neptune's atmosphere can change very quickly. When Voyager 2 flew past the planet in 1989 the dark spots were gone.

Like the other giant planets, Neptune is a ball of gas. The atmosphere is made up of frozen methane , which gives the planet its blue color. The planet has 8 known satellites. The biggest moon is Triton - about the same size as our own moon. It has active ice volcanoes. When they erupt, they shoot frozen nitrogen and gas about 20 km high.

Artits's impression of Neptune and one of its small moons
Image :ESA/Hubble, CC BY 4.0,
via Wikimedia Commons