From Neptune, the Sun is far away, 30 times more than Earth, and only seems a very bright spot. All other planets are between him and the Sun, at enormous distances, so that they are not seen.
But Neptune had a surprise. On October 10, 1846, less than three weeks after the discovery of Neptune, astronomer William Lassell discovered that he had a satellite, and shone brighter than the two Uranus satellites known until then.
Until July 2018, a total of 14 satellites of Neptune had been discovered. These are the most important ordered by their distance to the planet:
|Neptune satellites||Radius (km)||Distance (km)|
This great neptune satellite It has a diameter of 2,700 km and turns 355,000 km from Neptune in just under 6 days.
Two characteristics make it special: it is the only large satellite that rotates in the opposite direction to the rotation of its planet and is the object of the Solar System where the coldest average temperature has been measured, 235 ° C below zero.
The orbit of Triton is inclined about 30º with respect to the plane of the orbit described by Neptune around the Sun. It is believed that this satellite is made up of a quarter of it by ice and three quarters of it by rock.
When he was captured by Neptune's gravity and forced to describe an elliptical orbit around the planet, Triton rotated on its axis much faster than it currently does. For about a billion years, Neptune's gravity slowed Triton's rotation and led him to describe a circular orbit. In turn, Triton slowed Neptune's rotation.
Its surface has few craters, but abundant cracks. It also presents icy plains and geographical accidents similar to volcanoes with diameters of up to 200 km. There are geysers that throw dark jets into the dim atmosphere. This may be because the sunlight vaporizes liquid nitrogen below the surface of Triton.
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|The planet Neptune: blue, distant and windy||Shepherd rings and satellites|