Far beyond Neptune, strange patterns in the Kuiper Belt suggest something massive may be hiding in darkness. This story ...

Planet 9, still invisible in every telescope pointed its way, survives as a hypothesis because the orbital math keeps pointing back to an unseen mass. I see a pattern that has become harder to dismiss ...

Astronomers believe there is a Planet Nine in the outer solar system beyond Neptune. A team led by Amos Chen from the National Tsing Hua University, is searching for Planet Nine’s heat signature. When ...

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 ...

The solar system may have a ninth planet after all. This one is 5,000 times bigger than outcast Pluto and billions of miles farther away, say scientists who presented "good evidence" for a ...