WASHINGTON (Reuters) -Just as Earth orbits the sun, most planets discovered beyond our solar system orbit a host star.

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 ...

A team of astronomers took an actual photo of the first-known baby planet discovered in a gap of a star's protoplanetary disk.

There are 8 planets in our solar system. The planets orbit the Sun in elliptical trajectories, and they are all different in size, composition, temperature, and characteristics. The planets can be ...

A new study suggests yet another theory for a possible extra planet in our solar system, likely of a size between Mercury and ...