An alternate explanation that fits the evidence is that Vesta was once part of a planet – but which planet that might been ...

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.

Discovered in 1930, Pluto was long considered our Solar System's ninth planet, but was unseated in 2006 after the discovery ...

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.

And Back - The Super Soldiers Defending the Kuiper Belt On April 7, 2016, the team running NASA’s New Horizons mission were ...

For years, astronomers have toyed with the idea that the Sun hides an extra planet so distant and dim that even the best ...

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

If Planet Nine does exist, it could help to explain some of the unique orbits of smaller objects in the Kuiper Belt – a region of icy debris – at the far reaches of our Solar System ...