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 ...

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 ...

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, ...

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 ...

The Solar System does not have a clear border. The influence of the Sun in certain domains is small enough for the Voyager probes to have escaped into interstellar space, but there are comets and ...

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 ...

If the object really is Planet Nine, it would be larger than Neptune and exist 700 times further from the sun than Earth. The best candidate yet for the elusive Planet Nine has been spotted in two ...

The find represents the first clear detection of a baby planet taking shape within a disc of dust and gas with multiple rings. The ground-breaking discovery was made using European Southern ...