Beyond the familiar planets lies a fascinating frontier filled with icy worlds, mysterious orbits, and cosmic curiosities.

Astronomers say they have evidence that there may be a hidden planet in our Solar System. Named 'Planet Y', the Earth-sized ...

Astronomers propose a new hypothetical planet, Planet Y, beyond Neptune, based on observed orbital anomalies in the Kuiper belt.

Even if life never took hold on Ceres, the discovery could help broaden the range of environments that could potentially be ...

WASHINGTON >> Scientists have identified an object about 435 miles wide inhabiting the frigid outer reaches of our solar system that might qualify as a dwarf planet, spotting it as it travels on a ...

Aliens may have been closer to Earth than first thought. New research from NASA reveals that Ceres, the dwarf planet in the ...

New models suggest that Ceres, the asteroid belt's largest object, once had a radioactive core that could have sustained life in the dwarf planet's hidden subsurface ocean billions of years ago.

A team of astronomers believe they may have discovered a new dwarf planet—just like Pluto—on the edge of our solar system. The object—which orbits out beyond Neptune—has been named "2017 OF201" by the ...

For three-quarters of a century, schoolkids learned that our solar system has nine planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

A new dwarf planet, discovered beyond Neptune and described as Pluto's 'cousin,' could void the hypothesis of a Planet X in our solar system.

The unusual orbit of a possible dwarf planet, known as 2017 OF201, makes it less likely that our solar system contains a hidden ninth “Planet X” ...