It's an evocative idea that has long bedeviled scientists: a huge and mysterious planet is lurking in the darkness at the ...

Discovery of a possible dwarf planet suggests our cosmic backyard holds many more secrets to uncover It is an evocative idea ...

The chance of a planet forming in the outer reaches of the solar system - a hypothetical Planet Nine - could be as high as 40 ...

Some astronomers say the strange, clustered orbits of icy rocks beyond Neptune indicate that something big is out there, ...

In the cold, dark outskirts of planetary systems far beyond the reach of the known planets, mysterious gas giants and ...

Learn how a possible ninth planet, the theoretical Planet X, could have acquired its wide orbit in the outer Solar System - a ...

Astronomers find evidence of a possible ninth planet beyond Neptune, reigniting the debate about the formation of the Solar ...

There’s a new frozen oddball orbiting the Sun, and it’s not your average space rock. It’s a planet—a minor one, to be ...

Astronomers have discovered a mysterious dwarf planet, 2017 OF201, far beyond Pluto. This discovery challenges existing ...

In the cold, distant reaches of the Solar System, far beyond Pluto, astronomers have just identified what could be a new ...

Astronomers have found a new minor planet beyond Pluto. This object, named 2017 OF201, is quite large. It orbits far from the ...

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