If you’ve been having trouble remembering how many planets are in the solar system after Pluto’s unceremonious demotion, get ready to revise your understanding of the universe again. New calculations from an international team of researchers suggest that there could be two unknown planets beyond Pluto.
In two new studies, published in the Monthly Notices of the Royal Astronomical Society, scientists from the University of Madrid and the University of Cambridge posit that two—or more—unknown planets are responsible for unusual behavior beyond Neptune. Objects in that far-flung ZIP code don’t act like they should: the paths they move along do not have the orbital inclinations and axes that astronomers would expect to see, based on current theory of what researchers call "trans-Neptunia<wbr/>n objects."
Unless, the astrophysicists posit, there’s something else out there, and, after considering the effects of the “Kozai mechanism”—the effect an object orbiting further out from a gravitational source can have one orbiting futher in—they now believe there are at least two mysterious planets at play.
“Our results may be truly revolutionary for astronomy,” says co-author Carlos de la Fuente Marcos in a news release. But, as the team says, this is still a hypothesis. To prove it, scientists will have to overcome two hurdles. Not only does the new theory challenge astrophysicists' current thinking about how the solar system came to be, but the sample size used in the study’s calculations contains only 13 objects.
However, the team promises that with a larger sample size—coming soon—and new research (a recently-discovered planet-in-process is much further away from a star than scientists suspected to be possible), they’ll soon have even more evidence that our solar system may be even bigger than thought.