There may be an alien planet lurking within Earth’s own solar system. If the hypothetical Planet Nine does indeed exist, the sun probably ripped the world away from another star long ago, a new study suggests. Nobody has seen Planet Nine; Batygin and Brown inferred its existence from the odd orbits of a half-dozen small bodies in the frigid zone beyond Neptune known as the Kuiper Belt.
http://www.space.com/33041-planet-nine-captured-exoplanet.html
