Over the past century, astronomers have speculated about the existence of a mysterious 9th planet lurking in the outer reaches of our Solar System. Although we've never directly observed the elusive ...

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 ...

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 ...