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The orbit of Uranus and Neptune helped scientists to discover Pluto. The mass of Pluto and its pull is too small to explain how Uranus and Neptune stay in their orbits. There are some ideas about something on the other side of Pluto which pulls on these other planets.

One of these ideas is a mysterious planet called planet X which may be pulling on the orbit of Uranus and Neptune. Another idea is a black hole. Another one is that the sun has a companion star which pulls on the planets.