A planetary system 116 light-years from Earth has a peculiar pattern. It could flip the script on how planets form, ...

The fourth planet in the system is a rocky world, while the second and third ones are gas planets.

Add Yahoo as a preferred source to see more of our stories on Google. An illustration showing Planet Nine, a hypothetical, undiscovered planet in our solar system. New research now suggests the ...

Astronomers have found a distant world that challenges planetary formation theory, with a rocky planet where gas giants should be.

Planet Y is the latest in a series of hypothetical solar system planets that scientists have proposed in recent years, all with slightly different characteristics but collectively believed to be ...