Neptune is the eighth planet from the . Like and it is a gas giant.
Image of Neptune from NASA, L. Sromovsky, and P. Fry (University of Wisconsin-Madison)
It contains a small rocky surrounded by an mantle of frozen , and . Its diameter is almost four times the ís. Neptune has a magnetic field. Unusually for a planet, the magnetic axis is tilted far from the rotation axis. It is thought that the field may originate in the mantle rather than the core. Neptune radiates almost 3 times more than it receives from the Sun. The origin of this energy is not understood.
The outer atmosphere is mainly and , with a little . The atmosphere contains clouds and large spots, somewhat like ís Great Red Spot except they change far quicker. The highest clouds contain crystals of methane ice. Lower ones may contain frozen ammonia or hydrogen sulfide. There is also a haze of hydrocarbons produced by the action of sunlight on methane.
Neptune has 8 moons and probably incomplete rings.
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