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 ...

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

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

The solar system consists of our star, the sun, and everything bound to it by gravity: the planets Mercury, Venus, Earth, ...

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

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.

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

The 950-foot hunk of primordial matter is classified as a "potentially hazardous asteroid," but that doesn't mean it has a ...

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

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