Neptune
Neptune the planet completes an orbit to 4.495 billion kilometers, or 30 astronomical units from the Sun, making it the most distant of the planets of the solar system (Pluto is no longer competing since she was demoted to the rank of world dwarf). Because of this distance, the planet has a long orbital period: 165 Earth years.
Neptune diameter of about 49 500 km, slightly smaller than Uranus, but even four times that of Earth. Neptune has against a top Uranus mass about 17 times the mass of Earth.
The atmosphere of Neptune
The planet consists essentially of hydrogen and helium. It contains a huge rock core liquid, water, ammonia and methane which represents two thirds of the diameter. The outer third is composed of hydrogen, helium, water and methane.
The outer surface of Neptune consists of thick layers of cloud and appear blue due to the presence of methane. These clouds move at speeds that can range up to 2000 kilometers per hour, a speed record for the solar system.
Breaking the monotony, there are also long white clouds composed of methane ice crystals, and large blue spots due to hurricanes similar to those of Jupiter
Neptune satellites and rings
Neptune has at least 13 satellites. The most interesting of these satellites is Triton, the only one massive enough to have achieved a spherical shape. It has a diameter of 2700 km and is surrounded by a thin atmosphere rich in nitrogen with traces of methane.
Voyager 2 are measured in 1989 the lowest temperature ever recorded on a solar system body: -236 degrees Celsius. Its surface covered with nitrogen ice is very complex, with some formations that look like geysers and may reject nitrogen to an altitude of 8 kilometers.
Triton moves in a retrograde orbit, that is to say in the opposite direction to the rotation of Neptune, which is very unusual. The most plausible explanation is that Triton was not formed at the same location as Neptune, but was probably captured by the gravitational pull of the planet in the distant past.
The observations also show that the satellite is approaching inexorably Neptune under the effect of tidal forces. It should eventually explode and give birth to a beautiful ring around the planet.
Note also that Neptune is surrounded by a series of thin rings probably composed of dust. These rings are irregular and have denser parts that give them the appearance of arcs. The first were detected from Earth during stellar occultations in the 1980s, others were discovered by Voyager 2 in 1989.
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