Hot on the heels of speculation that the mysterious and yet-unproven Planet Nine causes a global extinction every 27 millions years as it passes through the Kuiper Belt and knocks comets at the Earth comes a new theory that the strange giant wasn’t always a part of our solar system and may have been stolen from another star. Put them together and this means our own Sun's criminal past was responsible for Earth’s mass extinctions. Say it ain’t so, Sol!

This ‘Capture the Planet’ theory comes from astronomers Alexandar Mustill at the Lund Observatory in Sweden and Greg Laughlin from the Lick Observatory in California. Starting with the premise that the Sun itself came from a dense cluster of thousands of stars, they wondered if that proximity would be close enough to steal planets from other stars.

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Possible orbit of alleged Planet Nine

To test the theory, they ran models and found that a star with a planet in a very wide orbit would lose it to the Sun 50 percent of the time. Those are coin flip odds, but before you go betting on the theory, they ran the models again while factoring in the probability that a close star would have a distant planet and the odds dropped substantially. Throw in the probability of the planet being exactly like Planet Nine is believed to be and the odds drop to 0.1 to 2 percent.

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The Pleiades star cluster shows a close proximity of stars that could facilitate planet stealing

That’s pretty low but, for you glass-half-full exoplanetary optimists, it’s not zero, says Mustill.

Although these probabilities seem low, you have to compare them to each other, and not absolutely. Because ultimately any very specific outcome is very unlikely.

Feeling a little ashamed that our Sun may have stolen a planet from another star? Mustill says it’s also possible that the star ejected the planet from its system due to an unstable orbit and our Sun picked up the abandoned orphan and gave it a new home.

Of course, we still don’t know with any certainty that Planet Nine exists at all. Until that time, Sol is innocent until proven guilty of stealing.

Paul Seaburn

Paul Seaburn is the editor at Mysterious Universe and its most prolific writer. He’s written for TV shows such as "The Tonight Show", "Politically Incorrect" and an award-winning children’s program. He's been published in “The New York Times" and "Huffington Post” and has co-authored numerous collections of trivia, puzzles and humor. His “What in the World!” podcast is a fun look at the latest weird and paranormal news, strange sports stories and odd trivia. Paul likes to add a bit of humor to each MU post he crafts. After all, the mysterious doesn't always have to be serious.

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