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 are closing in on one of the most tantalizing possibilities in planetary science, evidence that a previously unknown world may be lurking in the outer reaches of the solar system. The ...

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

Planetary systems in the Milky Way galaxy tend to follow a particular pattern: rocky planets toward the center, closest to ...

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