Is planet X real? Please cite information if it is factual.

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Planet X was a hypothesis created by Percival Lowell to help explain anomalies in the orbits of the gas giants.  He speculated that "the gravity of a large unseen ninth planet could have perturbed Uranus enough to account for the orbital irregularities." In 1930 the planet Pluto was discovered. Many thought this discovery proved Lowell's hypothesis.  It was not until the early 1990s that Voyager 2 identified "that the irregularities observed in Uranus's orbit were due to a slight overestimation of Neptune's mass."

Now in popular culture, and even among some astronomers, Planet X has become a "stand-in" term for any undiscovered planet in the outer

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