A huge planet thought to lurk on the outskirts of our solar system could upend the way we understand our cosmic neighborhood.
New evidence suggests that a never-before-observed large planet between the sizes of Earth and Neptune may be circling the sun once every 10,000 to 20,000 Earth years. If directly observed, this planet — nicknamed Planet Nine — could fill in a gap in our solar system that makes our place in the context of the Milky Way just a little more clear.
Planet Nine "makes our solar system more like the other planetary systems we've been finding throughout the galaxy than it was before," Mike Brown, co-author of a new study in the Astronomical Journal detailing the possible planet told Mashable in an interview.
"Throughout the galaxy, the most common type of planet is between the mass of the Earth and the mass of Neptune, and isn't it weird that we don't have this type of planet? And, it turns out, this is exactly what we have."
Brown and co-author Konstantin Batygin found evidence for the planet's existence in the strangely perturbed orbits of a handful of objects detailed in a previously published study. The objects are in the part of space known as the Kuiper Belt — the mass of icy bodies orbiting the sun from Pluto's part of space.
The six objects seem to move in their elliptical orbits all while pointing in the same direction, yet they move at different rates. All of the objects are tilted about 30 degrees in the same direction, the new study suggests.
"It's almost like having six hands on a clock all moving at different rates, and when you happen to look up, they're all in exactly the same place," Brown said in a statement.
"Basically it shouldn't happen randomly. So we thought something else must be shaping these orbits."
Brown — who tweets under the handle @plutokiller — has quite the history of making bold proclamations about the state of the far bits of the solar system. He was at least partially responsible for the "demotion" of Pluto in 2006 from major planet to dwarf planet with his discovery of the dwarf planet Eris, an object around the same size as Pluto, in the Kuiper Belt.
Now that some evidence for the world has been discovered, Brown thinks that it's possible observers will be able to confirm the planet's existence in about five years.
It could take them longer to rule out the planet's existence, however.
Could it be a planet?
This study is another in a rich history of scientists suggesting evidence for a Planet Nine.
Some theorists have long-predicted that some kind of large planet could be roaming the far-flung parts of the solar system, messing with the orbits of less massive bodies as they make their ways around the sun.
Alan Stern, principal investigator on the New Horizons mission that flew past Pluto in July, thinks that this study represents another step on a continuum of research that points to the idea of a large planet in the outer part of the solar system.
He also takes issue with the idea that this planet should be nicknamed "Planet Nine." Stern is a proponent of the idea that there are many, many planets in the solar system and we shouldn't expect to be able to name them all — just as people can't name every river or mountain on Earth.
"I think it's going to be a lesson of 21st Century astronomy," Stern told Mashable in an interview. "The number of planets in our own solar system is going to explode. I think people will get over worrying about their names."
Stern thinks that dwarf planets like Pluto, despite their small size, should also be called planets, even if they aren't as large as Earth or other "major planets" in the solar system.
According to Stern, some research suggests that there were once more large planets in the solar system that may have been thrown out, but it's likely that some of those planets stuck around in far-off orbits like this theoretical planet, he added.
"It would confirm that long-held belief that I and other theorists have had that the majority of the planets are far beyond the classical ones we grew up with," Stern said.
"It would confirm our models of solar system formation, that the solar system was very good at making large numbers of planets, but that most of them were ejected from the inner regions out ... where they're hard to find."