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 ...

There may be a warp in the Kuiper Belt, possibly caused by “Planet Y” — a Mercury-to-Earth-sized world that orbits the sun way beyond the orbit of Neptune. Is there a mysterious “Planet Y” orbiting ...

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