A planet four times the size of Earth may be skirting the edges of the solar system beyond Pluto, according to new research. Too distant to be easily spotted by Earth-based telescopes, the unseen planet could be gravitationally tugging on small icy objects past Neptune, helping explain the mystery of those objects' peculiar orbits.
The claim comes from Rodney Gomes, a noted astronomer at the National Observatory of Brazil in Rio de Janeiro.
http://www.space.com/15822-planet-edge-solar-system.html