[Michael E. Brown, t]he astronomer whose work helped kick Pluto out of the pantheon of planets says he has good reason to believe there’s an undiscovered planet bigger than Earth lurking in the distant reaches of our solar system.”
The Washington Post: New evidence suggests a ninth planet lurking at the edge of the solar system.
“[T]he authors, astronomers Michael Brown and Konstantin Batygin, have not observed the planet directly.
Instead, they have inferred its existence from the motion of recently discovered dwarf planets and other small objects in the outer solar system. Those smaller bodies have orbits that appear to be influenced by the gravity of a hidden planet”.
See the original paper here:
The Astronomical Journal: Evidence for a Distnad Giant Planet in the Solar Symste. By Konstantin Batygin and Michael E. Brown.
Abstract: “Recent analyses have shown that distant orbits within the scattered disk population of the Kuiper Belt exhibit an unexpected clustering in their respective arguments of perihelion. While several hypotheses have been put forward to explain this alignment, to date, a theoretical model that can successfully account for the observations remains elusive. In this work we show that the orbits of distant Kuiper Belt objects (KBOs) cluster not only in argument of perihelion, but also in physical space. We demonstrate that the perihelion positions and orbital planes of the objects are tightly confined and that such a clustering has only a probability of 0.007% to be due to chance, thus requiring a dynamical origin. We find that the observed orbital alignment can be maintained by a distant eccentric planet with mass [around ten times the mass of Earth …].”
Some links via MetaFilter: Many Very Educated Men Just Screwed Up Nature. Possibly?.