Over the past century, astronomers have speculated about the existence of a mysterious 9th planet lurking in the outer ...

We’re closer than ever before to knowing whether there is a ninth planet whooshing around the sun – and, alas, it’s not Pluto. Planet X, also called Planet Nine, is a hypothetical planetary body seven ...

A possible cousin of Pluto seems to be circling the far reaches of the solar system. The dwarf planet candidate 2017 OF201 travels in a superwide orbit, with the sun relatively near one end of its ...

Forbes contributors publish independent expert analyses and insights. An award-winning reporter writing about stargazing and the night sky. Is there an unseen planet — a "planet X" or "Planet Nine" — ...

(CNN) — While searching for the mysterious Planet X that some astronomers believe lurks on the edge of our solar system, researchers instead found an extremely distant object they dubbed "the Goblin." ...

Mike Brown is convinced that beyond Neptune, at the far reaches of our solar system, there's an unseen giant planet. "This is the 5th largest planet in our solar system, lurking out there, waiting to ...