Far beyond Neptune, something heavy appears to be tugging on the outer solar system, bending the paths of distant icy worlds in ways gravity alone should be able to explain. Planet 9, still invisible ...

After studying thousands of computer simulations of the solar system, researchers at Rice University and the Planetary Science Institute think there’s a 40% chance an elusive “Planet Nine” or “Planet ...

Astronomers have discovered a brand-new world hiding out beyond Pluto. While exciting, the discovery of this new world could challenge long-standing theories of the existence of Planet Nine. In fact, ...

Ian Whittaker does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond ...

Is there a massive undiscovered planet on the outer reaches of the solar system? The idea has been around since before the discovery of Pluto in the 1930s. Labeled as planet X, prominent astronomers ...