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

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.

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

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

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

Earth has four seasons, but do other planets in our solar system also have hot summer days and cold winter nights?

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

Scientists think they’ve detected a new planet beyond Neptune. Find out why experts believe 'Planet X' might support alien ...

Our solar system may have a ninth planet after all ... an unusual clustering of icy bodies -- including comets and dwarf planets -- which stretches from Neptune and outward toward interstellar ...