Astronomers propose a new hypothetical planet, Planet Y, beyond Neptune, based on observed orbital anomalies in the Kuiper ...

A mysterious new world may be hiding in the outer reaches of our solar system. According to arecent study published on arXiv ...

Far beyond Neptune, astronomers believe a mysterious giant planet is hiding in the darkness. Known as Planet 9, this world ...

Planet Nine was previously suggested as a possible explanation for distant orbital clustering. It was thought to be ten times Earth’s mass, orbiting far beyond Neptune.

CAPE CANAVERAL, Fla. - The solar system may host a ninth planet that is about 10 times bigger than Earth and orbiting far beyond Neptune, according to research published on Wednesday.

Neptune, long believed to be dark blue, is actually very pale like Uranus, scientists say. They used modern telescopes to re-assess artificially enhanced images taken by NASA's Voyager 2 probe.

Neptune, one of our most distant planetary neighbors, may not be the color we've always thought it was. Previous images of far-off planets showed Neptune as being a deep electric blue, while ...

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 ...