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

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

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.

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.

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

Vesta had been thought to have been the last protoplanet, a leftover remnant from the early days of our solar system that never quite made it as a fully fledged planet for some reason. As the ...

Indeed, other planets, dwarf planets and moons in our solar system do have seasonal cycles — and they can look wildly different from the ones we experience on Earth, experts told Live Science.