Another Planet Past Pluto?

Could there be another planet out there, which is part of our Solar System?

Researchers at Caltech seem to think so.
They believe it has a mass about 10 times that of Earth and orbits about 20 times farther from the sun on average than does Neptune (which orbits the sun at an average distance of 2.8 billion miles)

We may have a 9th planet (again! – after the demotion of Pluto).
The hunt begins.

Read more at the Caltech media release.

Response from Jim Green at NASA