CBS: Astronomers Find Evidence of a Ninth Planet in Our Solar System

Astronomers find evidence for yet-unseen "Planet Nine" (CBS News) 

Researchers trying to figure out how a handful of bodies in the remote Kuiper Belt beyond Pluto ended up in unusual, similarly oriented elliptical orbits believe the most likely explanation is the gravitational influence of a hitherto undetected planet with 10 times the mass of Earth that orbits 20 times farther from the sun than Neptune, they announced Wednesday.

California Institute of Technology astronomers Konstantin Batygin, a theoretician, and Mike Brown, discover of multiple dwarf planets in the outer solar system and a vocal proponent of Pluto's demotion from planet-hood, conclude the as-yet-unseen world, which they call "Planet Nine," would take between 10,000 and 20,000 years to complete one trip around the sun.

"It's big enough, and probably reflective enough, that it should be relatively bright," Brown told CBS News in a telephone interview. "We know the orbit, but we don't know where in the orbit it is."