In a paper published today in the Astronomical Journal, astronomers Michael E. Brown and Konstantin Batygin report that there is new evidence that suggests the presence of a giant icy planet at the edge of our solar system that is 10 times the mass of Earth. 

The new planet, dubbed "Planet Nine," hasn't been observed directly, but The Washington Post writes that Brown and Batygin have "inferred its existence from the motion of recently discovered dwarf planets and other small objects in the outer solar system." The orbits of the small planets appear to be affected by the gravity of the larger Planet Nine, which is believed to have an "estimated mass would make it about two to four times the diameter of the Earth, distinguishing it as the fifth-largest planet after Jupiter, Saturn, Uranus, and Neptune," the paper notes. Scientists are currently searching for the new planet, but with an estimated distance 20 times farther than Neptune, it may not reflect enough sunlight to be seen by even the most powerful telescopes. 

Michael E. Brown, the "Pluto Killer" astronomer whose discovery of the dwarf planet Eris led to the reclassification of Pluto by the International Astronomical Union, spoke with the Post about Planet Nine and the possibility that it could one day take the former ninth planet's place. Brown explains that scientists cannot yet say that Planet Nine was "discovered" because "discovery means it’s been seen. Someone has seen it, has seen it move, has seen the orbit. We think we know the orbit, but we don't know where on that orbit the planet is, and we haven't seen it yet. This paper we published is like handing everyone a treasure map."