There’s a new object in the distant reaches of our solar system, and it might just offer clues to a long-standing cosmic ...

Today, it’s believed that Jupiter and Saturn, the largest planets, were the first to fully form, both within a few million ...

Learn about the recently discovered trans-Neptunian object that may eventually join Pluto as a dwarf planet, found at the ...

A recent study found that Jupiter was once twice the size that it is now, making it big enough to swallow up 2,000 Earths.

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 ...

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

For decades, our solar system was thought to have nine planets, with Pluto considered the smallest and farthest. But in 2006, ...

Christopher Palma does not work for ... the first thing to form in our solar system. This happened about 4½ billion years ago. Then the planets began to emerge, as the billions of particles ...

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

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

Our solar system may have a ninth planet after all, following the declassification of Pluto nearly two decades ago, researchers say.

A team of astronomers believe they may have discovered a new dwarf planet—just like Pluto—on the edge of our solar system.