Planet Nine is a theoretical, undiscovered giant planet in the mysterious far reaches of our solar system. The presence of Planet Nine has been hypothesized to explain everything from the tilt of the ...

Pluto's status as our solar system's ninth planet may be safe if a recently discovered Kuiper Belt Object is a typical "KBO" and not just an oddball. Astronomers have new evidence that ...

The Kuiper belt, a disc of icy rocks on the outermost edges of the solar system, seems to have more structure than we thought. In 2011, researchers found a cluster of objects there on similar orbits ...