For over a century, scientists have suspected there could be a hidden planet lurking far beyond Neptune—massive enough to ...

A mysterious new world may be hiding in the outer reaches of our solar system. According to arecent study published on arXiv by Amir Siraj of Princeton University and colleagues, a previously unknown ...

Add Yahoo as a preferred source to see more of our stories on Google. A mysterious "rogue planet" has been observed gobbling 6 billion tons of gas and dust a second — an unprecedented rate that blurs ...

There may be a warp in the Kuiper Belt, possibly caused by “Planet Y” — a Mercury-to-Earth-sized world that orbits the sun way beyond the orbit of Neptune. Is there a mysterious “Planet Y” orbiting ...