Our solar system may have a ninth planet after all, following the declassification of Pluto nearly two decades ago, ...

If the object really is Planet Nine, it would be larger than Neptune and exist 700 times further from the sun than Earth.

A team of astronomers believes they may have spotted a serious candidate for a ninth planet in our Solar System. This object, ...

Using two infrared space telescopes and a 23-year gap, scientists may have spotted a mysterious, slow-moving object beyond ...

Astronomers have long speculated about an unseen planet lurking in the solar system's outer edge. This hypothetical world, ...

The presence of another planet in the solar system could explain the odd movements of some of the bodies in the Kuiper Belt.

Astronomers searching for a ninth planet in our solar system say they've found a "good" candidate far beyond Neptune, ...

A ninth planet the size of Neptune may be hidden in the far reaches of the solar system, but the evidence has left some experts skeptical.

Researchers say they found a curious dot on infrared images taken 23 years apart that seems to be moving in a manner consistent with a large, distant planet.

A new look through decades-old data has unveiled some of the most compelling evidence yet of a hidden ninth planet in the far ...

Astronomers may have found a candidate for Planet Nine. This planet is beyond Neptune. The finding could be the first ...