Astronomers have searched for Planet X for over a century without success. This video explains why distance, darkness, and technology make it so hard to detect distant worlds. It shows how past ...

The curious minds at What If predict the effects if Planet X entered our solar system, revealing orbital chaos, climate changes, and planetary disruption.

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 ...

A new study has proposed the existence of Planet Y, an alternative Planet Nine candidate that is smaller and closer to Earth than the hypothetical Planet X, which astronomers have been hunting for ...