Astronomers are closing in on one of the most tantalizing possibilities in planetary science, evidence that a previously ...

An artist's concept depicting the pulsar planet system. (Photo by: Universal History Archive/Universal Images Group via Getty Images) Rarely even acknowledged as the first planets discovered beyond ...

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

LONDON — 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 ...

A leading scientist has told Newsweek about new evidence supporting the existence of a secret ninth planet lurking at the edge of our solar system. This hypothetical extra planet, often referred to as ...

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 ...