Discovery of Triton

Triton was discovered by the English astronomer William Lassell, a brewer who built his own telescopes in Liverpool, only seventeen days after Neptune itself had been found. It is the largest moon of Neptune, and it moves in a retrograde orbit, in the opposite direction to the planet's rotation, which strongly suggests that it was captured from the Kuiper belt and did not form near Neptune. In 1989 Voyager 2 flew past and discovered a young surface of nitrogen ice with active geysers and one of the coldest temperatures measured in the solar system. Because its orbit is slowly decaying, Triton will eventually be torn apart by tidal forces or hit Neptune, but that is billions of years away.

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