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

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

Astronomers have picked up evidence of an Earth-sized world, distinct from the previously hypothesised Planet Nine and Planet ...

Only eight planets call our solar system home. Or there might still be nine if some astronomers are correct about an as-yet undiscovered large body out past Neptune.

A newly discovered object called 2017 OF201, likely a dwarf planet, travels in an extremely wide elliptical orbit (yellow), a new study suggests. The orbit of the dwarf planets Sedna and Pluto are ...

Though Pluto has formally been considered a dwarf planet for almost two decades, it still has many lessons left for planetary scientists — including hints about how the solar system formed.

This process, called accretion, is how everything in the solar system – planets, moons, comets and asteroids – came into being. Telescopes can see young solar systems being born.

Today there are five known dwarf planets in the Solar System. The conditions for what classifies a “planet” as opposed to a “dwarf planet” were set by the International Astronomical Union.

In fact, researchers have spent decades combing the night sky for evidence of other planets at the far end of our own solar system. In February, researchers announced they had narrowed the search ...