It's an evocative idea that has long bedeviled scientists: a huge and mysterious planet is lurking in the darkness at the edge of our solar system, evading all our efforts to spot it. Some astronomers ...

"It's almost unfathomable to imagine what is happening to this planet. The planet's atmosphere simply cannot withstand the high X-ray dose it's receiving from its star." Using NASA's Chandra X-ray ...

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 ...

Astronomers used a telescope in Hawaii to find a new object on the outer edges of our solar system, helping to fuel evidence of a long-standing theory about Planet Nine, or Planet X. For years, ...

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 ...

For almost a decade, astronomers have been searching for a ninth planet in the solar system. Recently, new evidence of another possible planet, dubbed Planet Y, was uncovered, and it could be around ...

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 ...

The first sign of possible extraterrestrials detected in the cosmos didn't come in the form of little green aliens flying around in saucer-shaped spacecraft. In fact, the life that could be – emphasis ...