For the first time since Pluto was demoted, the idea of a true ninth planet is edging from speculation toward something ...

There have been questions about a mysterious ninth planet in our solar system for nearly a decade. Pluto was unseated as number nine in 2006. Now, a group of international researchers say they may ...

Far beyond Neptune, something heavy appears to be tugging on the outer solar system, bending the paths of distant icy worlds ...

Subscribe to The St. Louis American‘s free weekly newsletter for critical stories, community voices, and insights that matter. Sign up (CNN) — You might have a replacement, Pluto. There could be ...

Astronomers searching for a ninth planet in our solar system say they've found a "good" candidate far beyond Neptune, according to a new preprint study. This could be humanity's first glimpse at the ...

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 ...

Caltech researchers have found evidence of a giant planet tracing a bizarre, highly elongated orbit in the distant solar system. The object, which the researchers have nicknamed Planet Nine, has a ...

(CNN)You might have a replacement, Pluto. There could be another planet in our solar system. Researchers at the California Institute of Technology have found evidence in the outer solar system of an ...