Planet X, a hidden giant seven times Earth’s mass, challenges astronomers with its faint light and distant orbit, potentially ...

After studying thousands of computer simulations of the solar system, researchers at Rice University and the Planetary Science Institute think there’s a 40% chance an elusive “Planet Nine” or “Planet ...

Over the past century, astronomers have speculated about the existence of a mysterious 9th planet lurking in the outer reaches of our solar system. Although we’ve never directly observed the elusive ...

Is there a massive undiscovered planet on the outer reaches of the solar system? The idea has been around since before the discovery of Pluto in the 1930s. Labeled as planet X, prominent astronomers ...

Astronomers used a telescope in Hawaii to find a new object on the outer edges of our solar system, helping to fuel evidence of a long-standing theory about Planet Nine, or Planet X. For years, ...