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 ...

LONDON — The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper's authors have ...

Even at a glance, the planets in our solar system are wildly diverse. Huge and small, airless and densely packed with ...

Astronomers believe they have uncovered evidence of a previously unknown ninth planet lurking in the not-too-distant reaches of the solar system. This hypothetical world, dubbed "Planet Y," could be ...