what is its origin?
One early hypothesis was that Pluto was an escaped moon of Neptune.
Pluto
 One early hypothesis was that Pluto was an escaped moon of Neptune
what is pluto? A dwarf planet in the Kuiper belt. who discovered it? Clyde Tombaugh when? 1930
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Pluto [SEP] Origin
Pluto's origin and identity had long puzzled astronomers. One early hypothesis was that Pluto was an escaped moon of Neptune, knocked out of orbit by its largest current moon, Triton. This idea was eventually rejected after dynamical studies showed it to be impossible because Pluto never approaches Neptune in its orbit. Pluto's true place in the Solar System began to reveal itself only in 1992, when astronomers began to find small icy objects beyond Neptune that were similar to Pluto not only in orbit but also in size and composition. This trans-Neptunian population is thought to be the source of many short-period comets.