Here's the paper:
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 gsim10 m⊕ whose orbit lies in approximately the same plane as those of the distant KBOs, but whose perihelion is 180° away from the perihelia of the minor bodies. In addition to accounting for the observed orbital alignment, the existence of such a planet naturally explains the presence of high-perihelion Sedna-like objects, as well as the known collection of high semimajor axis objects with inclinations between 60° and 150° whose origin was previously unclear. Continued analysis of both distant and highly inclined outer solar system objects provides the opportunity for testing our hypothesis as well as further constraining the orbital elements and mass of the distant planet.
New York Times: Ninth Planet May Exist in Solar System Beyond Pluto, Scientists Report
[...]
"We are pretty sure there's one out there," said Michael E. Brown, a professor of planetary astronomy at the California Institute of Technology.
What Dr. Brown and a fellow Caltech professor, Konstantin Batygin, have not done is actually find that planet, so it would be premature to revise mnemonics of the planets just yet.
Rather, in a paper published Wednesday in The Astronomical Journal, Dr. Brown and Dr. Batygin lay out a detailed circumstantial argument for the planet's existence in what astronomers have observed — a half-dozen small bodies in distant, highly elliptical orbits.
What is striking, the scientists said, is that the orbits of all six loop outward in the same quadrant of the solar system and are tilted at about the same angle. The odds of that happening by chance are about 1 in 14,000, Dr. Batygin said.
[...]
First, they focused on the six objects in stable orbits and disregarded objects that had been recently flung out by Neptune to eventually depart the solar system.
That made the picture clearer.
"What we realized is the story is much more simple and more fundamental," Dr. Batygin said. "They all point into the same overall direction. All in same quadrant. This is in stark contrast with the rest of the Kuiper belt."
Besides the long odds of this alignment being coincidental, Dr. Batygin said, this pattern would not last indefinitely, dispersing over a few hundred million years — a short time compared to the 4.5 billion-year age of the solar system.
"We're not observing a relic of a perturbation of the past," he said.
That argued for something else, something bigger, that is currently guiding Sedna and the others.
Dr. Batygin, a theorist, tried placing a planet among the six objects. That did scatter some of the Kuiper belt objects, but the orbits were not sufficiently eccentric.
Then he examined what would happen if a ninth planet were looping outward in a direction opposite to Sedna and the others. That, Dr. Batygin said, gave "a beautiful match to the real data."
The computer simulations showed that the planet swept up the Kuiper belt objects and placed them only temporarily in the elliptical orbits. Come back in half a billion years, Dr. Brown said, and Sedna will be back in the Kuiper belt, while other Kuiper belt objects will have been swept into similar elliptical orbits.
Another strange result in the simulations: A few Kuiper belt objects were knocked into orbits perpendicular to the plane of planetary orbits. Dr. Brown remembered that five objects had been found in perpendicular orbits.
"They're exactly where we predicted them to be," Dr. Brown said. "That's when my jaw hit my floor. I think this is actually right."
Dr. Trujillo said the new paper made a much more convincing argument for another planet than his own did. "We're pleasantly surprised that someone has really done a much better job than we did," he said.
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 gsim10 m⊕ whose orbit lies in approximately the same plane as those of the distant KBOs, but whose perihelion is 180° away from the perihelia of the minor bodies. In addition to accounting for the observed orbital alignment, the existence of such a planet naturally explains the presence of high-perihelion Sedna-like objects, as well as the known collection of high semimajor axis objects with inclinations between 60° and 150° whose origin was previously unclear. Continued analysis of both distant and highly inclined outer solar system objects provides the opportunity for testing our hypothesis as well as further constraining the orbital elements and mass of the distant planet.
New York Times: Ninth Planet May Exist in Solar System Beyond Pluto, Scientists Report
[...]
"We are pretty sure there's one out there," said Michael E. Brown, a professor of planetary astronomy at the California Institute of Technology.
What Dr. Brown and a fellow Caltech professor, Konstantin Batygin, have not done is actually find that planet, so it would be premature to revise mnemonics of the planets just yet.
Rather, in a paper published Wednesday in The Astronomical Journal, Dr. Brown and Dr. Batygin lay out a detailed circumstantial argument for the planet's existence in what astronomers have observed — a half-dozen small bodies in distant, highly elliptical orbits.
What is striking, the scientists said, is that the orbits of all six loop outward in the same quadrant of the solar system and are tilted at about the same angle. The odds of that happening by chance are about 1 in 14,000, Dr. Batygin said.
[...]
First, they focused on the six objects in stable orbits and disregarded objects that had been recently flung out by Neptune to eventually depart the solar system.
That made the picture clearer.
"What we realized is the story is much more simple and more fundamental," Dr. Batygin said. "They all point into the same overall direction. All in same quadrant. This is in stark contrast with the rest of the Kuiper belt."
Besides the long odds of this alignment being coincidental, Dr. Batygin said, this pattern would not last indefinitely, dispersing over a few hundred million years — a short time compared to the 4.5 billion-year age of the solar system.
"We're not observing a relic of a perturbation of the past," he said.
That argued for something else, something bigger, that is currently guiding Sedna and the others.
Dr. Batygin, a theorist, tried placing a planet among the six objects. That did scatter some of the Kuiper belt objects, but the orbits were not sufficiently eccentric.
Then he examined what would happen if a ninth planet were looping outward in a direction opposite to Sedna and the others. That, Dr. Batygin said, gave "a beautiful match to the real data."
The computer simulations showed that the planet swept up the Kuiper belt objects and placed them only temporarily in the elliptical orbits. Come back in half a billion years, Dr. Brown said, and Sedna will be back in the Kuiper belt, while other Kuiper belt objects will have been swept into similar elliptical orbits.
Another strange result in the simulations: A few Kuiper belt objects were knocked into orbits perpendicular to the plane of planetary orbits. Dr. Brown remembered that five objects had been found in perpendicular orbits.
"They're exactly where we predicted them to be," Dr. Brown said. "That's when my jaw hit my floor. I think this is actually right."
Dr. Trujillo said the new paper made a much more convincing argument for another planet than his own did. "We're pleasantly surprised that someone has really done a much better job than we did," he said.
