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 ...

"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 ...

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 ...

A mysterious new world may be hiding in the outer reaches of our solar system. According to arecent study published on arXiv by Amir Siraj of Princeton University and colleagues, a previously unknown ...

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 ...