Earlier this month, NASA issued a press release stating that it’s likely that our solar system has a ninth planet—even if it’s proving difficult to find.

The planet could have a mass ten times that of Earth’s, and be situated twenty times as far from the sun as Neptune. It’s being referred to as “Planet Nine,” and while it’s very difficult to procure clear evidence of its existence, some scientists are absolutely convinced that it’s out there.

“There are now five different lines of observational evidence pointing to the existence of Planet Nine,” said Konstantin Batygin, a planetary astrophysicist at the California Institute of Technology (Caltech), who is part of a team on the search for the planet.

“If you were to remove this explanation and imagine Planet Nine does not exist, then you generate more problems than you solve. All of a sudden, you have five different puzzles, and you must come up with five different theories to explain them.”

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