Astronomers from the Lund University in Sweden believe that Planet 9 was probably stolen by our own sun from its original star. The findings, published on April 26 in the journal Monthly Notices of the Royal Astronomical Society, state that this occurred 4.5 billion years ago when the young sun came in close contact with Planet 9’s star.

“Planet 9 may very well have been ‘shoved’ by other planets, and when it ended up in an orbit that was too wide around its own star, our sun may have taken the opportunity to steal and capture Planet 9 from its original star,” says Alexander Mustill, an astronomer at Lund University. “When the sun later departed from the stellar cluster in which it was born, Planet 9 was stuck in an orbit around the sun.”

Since then, Planet 9 may have been a part of our own solar system but is somehow undetectable. This indicates that Planet 9 would be the first exoplanet found inside the solar system. An exoplanet is a planet situated outside our solar system.

“It is almost ironic that while astronomers often find exoplanets hundreds of light years away in other solar systems,” adds Mustill. “There’s probably one hiding in our own backyard.”

The research team created a computer simulation that replicated the stars coming in close contact. Still, despite these interests surrounding Planet 9, no one knows what it looks like. “There is still no image of Planet 9, not even a point of light. We don’t know if it is made up of rock, ice, or gas,” Mustill points out. “All we know is that its mass is probably around ten times the mass of earth.”

The researchers assert that more investigations are needed to confirm the exoplanet’s existence. Nevertheless, if this theory turns out to be true, science books will be in need of a huge overhaul.