Those with a Pluto-the-planet-shaped void in their hearts have been eagerly following updates about Planet 9, a hypothetical world thought to be 10 times more massive than Earth and roughly 1,000 astronomical units (AU) away from the Sun. While there are naysayers aplenty, new research validates believers — and delivers some unexpected news about the planet’s rough childhood.
Space.com reports that after months of research, James Vesper, an undergraduate student at New Mexico State University (NMSU), announced at the 229th gathering of American Astronomical Society (AAS) it’s “very plausible” that Planet 9 was a “rogue planet”—a planetary-mass object that wanders around the galaxy unattached to a star. If he’s right, this would mean our Sun snatched the unsuspecting planet like a cosmic Hamburglar stealing a snack.
Vesper and his mentor, NMSU professor Paul Mason, came to this conclusion after running 156 simulations of possible encounters between our Sun and various rogue planets. Vesper said that in about 60 percent of the encounters, the incoming rogue planet would enter the solar system and eventually get ejected. But, in 40 percent of the simulations, the rogue was captured by the solar system and stayed put—sometimes booting another planet out of orbit in the process. It’s not a definitive explanation of Planet 9's origin, or a confirmation of its existence, but it’s certainly feasible.
The fact that rogue planets are abundant—possibly even more so than the number of planets with suns—also bolsters Vesper and Mason’s argument.
At this point, Planet 9, rogue or not, is still a pile of hypotheticals. But Konstantin Batygin, an assistant professor of planetary sciences at Caltech, thinks Vesper’s findings could be legit.
“It is certainly plausible that Planet 9 is captured object,” Batygin, who has pioneered research around the hypothetical world, told Gizmodo. “Without knowing the precise orbit, it is difficult to decisively confirm or refute rogue capture as Planet 9’s origin story, but it’s certainly possible.”
Regardless of its origins, Batygin said we should remain curious about this weird world.
“I’m quite certain that Planet 9 is really out there,” he said. “The number of seemingly unrelated puzzles within the solar system that are resolved by Planet 9’s existence is simply too great for it all to be a coincidence.”