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 ...

Add Yahoo as a preferred source to see more of our stories on Google. This artist’s illustration provided by the European Southern Observatory shows an exoplanet orbiting around two brown dwarfs, ...

Astronomers studying the Kuiper Belt have detected a strange distortion that could point to an unknown planet lurking far beyond Neptune.

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to ...

The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper’s authors have dubbed ...

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 ...