California Institute of Technology scientists Konstantin Batygin and Mike Brown noticed that objects in the Kuiper Belt, a field of ice and debris beyond Neptune—currently the 8th and final recognized planet in our solar system—have orbits that point in the same direction.
Mathematical modeling and computer simulation led Batygin and Brown to believe that a planet was responsible for this gravitational pull, although they have yet to actually catch a glimpse of this planet.
"We could have stayed quiet and quietly spent the next five years searching the skies ourselves and hoping to find it. But I would rather somebody find it sooner, than me find it later," Brown told the Associated Press.
All that's known of Planet Nine is its rough orbit, and the scientists predict it could take up to five years to pinpoint a precise location.
Planet Nine "has a mass about 10 times that of Earth" and it would take the planet "between 10,000 and 20,000 years to make just one full orbit around the sun," said a Caltech spokesperson.
This means the object would be classed as a planet, unlike Pluto, which Brown helped to reclassify as a dwarf planet back in 2006.
The scientists hypothesize it is 5,000 times the size of Pluto and roughly 20 to 100 billion miles away from Earth at the edge of our solar system.
"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," Brown said. Now we can go and find this planet and make the solar system have nine planets once again."
A new planet has not been discovered since Neptune in 1846, so the potential discovery is big news for the scientific community.
"There have only been two true planets discovered since ancient times, and this would be a third," Brown said. "It's a pretty substantial chunk of our solar system that's still out there to be found, which is pretty exciting."
Reach staff reporter Taylor Edgehill here.