The planet Neptune was discovered in 1846. Ever since then, astronomers have felt there had to be another planet beyond the orbit of Neptune. Everyone assumed they found it with the discovery of Pluto in 1930, however, something still wasn’t quite right. 90 years later, the mystery planet hasn’t been found, but astronomers might be getting close. Learn more about Planet Nine, sometimes known as Planet X, on this episode of Everything Everywhere Daily.

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