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The 170-Year Search for a Planet Beyond Neptune

There may be a ninth planet at the edge of our solar system — it’s not Pluto and it’s not “Planet X.”

Publish Date: Topic: Space + FlightSpace & FlightNova
By Ana Aceves and Caitlin Saks

Planet Nine’s existence is not the first time astronomers have predicted a planet they couldn’t see. Clyde Tombaugh was looking for Planet X when he accidentally found Pluto. After Voyager 2 flew by Neptune in 1989, new calculations determined there was no Planet X. But three years ago, a disturbance was detected at the far reaches of the Solar System.

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