For the first time since Pluto was demoted, the idea of a true ninth planet is edging from speculation toward something ...

Far beyond Neptune, something heavy appears to be tugging on the outer solar system, bending the paths of distant icy worlds ...

Astronomers used a telescope in Hawaii to find a new object on the outer edges of our solar system, helping to fuel evidence of a long-standing theory about Planet Nine, or Planet X. For years, ...

There may be more ringed objects in the outer solar system than anyone knew. This week, researchers revealed that the egg-shaped dwarf planet Haumea — one of four known diminutive planets that circle ...

The newly identified cluster of Kuiper Belt objects lies about 4 billion miles from the Sun, offering fresh clues about how ...

Scientists may have missed the mark when they started referring to Uranus and Neptune as the "ice giant" planets of the solar system decades ago. Like giving a certain short-armed dinosaur a name that ...

The Hubble Space Telescope has peered at Uranus, left, and Neptune to study the so-called "ice giant" planets, but little is known about their interior composition. Credit: NASA / ESA / M. Showalter / ...

A team of astronomers has announced the discovery of some of the smallest planets yet detected beyond our solar system. The two newly discovered planets represent a new class of extrasolar planets, ...