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 ...

Over the past century, astronomers have speculated about the existence of a mysterious 9th planet lurking in the outer reaches of our solar system. Although we’ve never directly observed the elusive ...

Planet Y: In a remarkable discovery that could reshape the prevalent scientific view of our solar system, astronomers have found evidence of a 'hidden' planet on the outskirts of our cosmic ...

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 ...

See more of our trusted coverage when you search. Prefer Newsweek on Google to see more of our trusted coverage when you search. Astronomers have discovered a brand new cold "super Jupiter" exoplanet, ...

The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper’s authors have dubbed ...

Astronomers have observed a planet that in some ways behaves more like a star — including a massive growth spurt unlike anything witnessed before in a free-floating planet. The rogue planet, which ...