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 ...

NEW YORK (AP) — For sale: A 54-pound (25-kilogram) rock. Estimated auction price: $2 million to $4 million. Why so expensive? It’s the largest piece of Mars ever found on Earth. Sotheby’s in New York ...