There are eight planets in our solar system, and have been officially ever since Pluto was reclassified as a dwarf planet in 2006. But what if there was a ninth planet, billions of miles past Neptune?
Earlier this year, researchers from CalTech announced that they had found signs of the planet, which is referred to a “Planet 9,” through modeling and computer simulations. If a ninth planet were out there, it would be a big one— ten times the mass of Earth— and very, very far away, completing just one orbit around the sun as slowly as perhaps every 10,000 to 20,000 years.
Now, scientists from Lund University in Sweden have used computer simulations to propose a new theory about how Planet 9— if it exists— came to be a member of the solar system. They propose that it was stolen by our sun from another star about 4.5 billion years ago.