Jupiter is already the biggest planet by far in our solar system, but new research suggests it was somehow once even larger than it is now. Twice as large, in fact. To put that into context, those ...

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 ...

WASHINGTON (Reuters) -In a memorable image from the 1977 film "Star Wars," the young hero Luke Skywalker gazes at two suns setting above the horizon on his desert planet Tatooine. Astronomers since ...

WASHINGTON (Reuters) -Astronomers have spotted a cosmic mismatch that has left them perplexed - a really big planet orbiting a really small star. The discovery defies current understanding of how ...