'Pluto Killer' Says We Might Have A 9th Planet After All

Two astronomers say there's probably a ninth planet that circles our sun. We just haven't seen it yet.

Caltech researchers Konstantin Batygin and Mike Brown say there's evidence a ninth planet is in the outer reaches of our solar system, with an orbit that takes up to 20,000 years to circle the sun. Batygin and Brown used mathematical models and computer simulations to determine that there is likely another large planet out there, but haven't actually seen it. "I would love to find it," said Brown in a press release from Caltech. "But I'd also be perfectly happy if someone else found it. That is why we're publishing this paper. We hope that other people are going to get inspired and start searching."

The irony is that Brown is the same astronomer who says he "killed Pluto" when his team discovered larger objects beyond Pluto, leading it to get downgraded to "dwarf planet."

"All those people who are mad that Pluto is no longer a planet can be thrilled to know that there is a real planet out there still to be found," said Brown. "Now we can go and find this planet and make the solar system have nine planets once again."

So why, exactly, do Batygin and Brown figure there's another planet out there? Two recently discovered objects in the Kuiper belt—dwarf planet 2012 VP113 and the 600-mile rock Sedna—had unusual orbits that suggested another large planet out there. The Kuiper belt is a disc of objects beyond the orbit of Neptune, including dwarf planets such as Pluto.

"Their orbits do not hug the orbit of Neptune, and hugging the orbit of Neptune is kind of a unifying feature among the vast population of Kuiper belt objects," Batygin told the L.A. Times. "Neptune could not have gravitationally kicked them out to an orbit with which it doesn’t interact." They looked closer at the orbits of four other Kuiper belt objects and determined that another large planet had to be out there.

This theoretical ninth planet is said to be a gas giant about 10 times larger than Earth, but smaller than Neptune. It's possible that when the solar system was forming, the ninth planet was flung into its current orbit by the gravitational influence of either Jupiter or Saturn.

Brown says that even though this ninth planet has not been directly observed, it's only a matter of time until one of the telescopes on Earth picks it up, especially since they have its theoretical orbit.

Watch this video, where Batygin and Brown explain their discovery.