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

Researchers have found a candidate for the hypothetical Planet Nine, which could be an undiscovered giant planet way out in ...

Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She's also an enthusiast of just about ...

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

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.

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

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

For over a century, astronomers have wondered if there's an extra planet in our Solar System that we haven't been able to see ...

A powerful new observatory is the best hope yet for finding the elusive Planet 9, a large planet that some scientists say is hidden in our solar system.

Planet Nine (or Planet X as NASA calls it) first emerged as a real possibility in 2016, when two astronomers from the California Institute of Technology presented evidence of a large gravitational ...