Our solar system may have a ninth planet after all, following the declassification of Pluto nearly two decades ago, ...

Researchers have found a candidate for the hypothetical Planet Nine, which could be an undiscovered giant planet way out in our solar system. However, as with all ninth planet research, the new ...

The presence of another planet in the solar system could explain the odd movements of some of the bodies in the Kuiper Belt.

A ninth planet the size of Neptune may be hidden in the far reaches of the solar system, but the evidence has left some experts skeptical.

A powerful new observatory is the best hope yet for finding the elusive Planet 9, a large planet that some scientists say is ...

Neptune and then the possible Planet Nine. It's a dynamic system shaped by gravity and time, and while we've learned a lot, it still holds plenty of mysteries. In this guide, we'll explore how the ...

and it got all too crazy. Viewed in this longer context, the previously modern idea of having nine planets, which came about in the 1960s and lasted only until 2006, was a blip on the screen.