Almost 10 years ago, a NASA spacecraft was able to take several photos of Pluto, known for decades as a planet before it was ...

Nevertheless, because it orbited the Sun like a planet, it was classified as a planet and named Pluto, after the god of outer darkness ... alone in its region of space, much as Ceres had seemed ...

In 2006, the International Astronomical Union (IAU) decided that a large celestial object is a planet only if its gravitational orbit around the sun makes it round and if it’s big enough to ...

The relative quantities of volatile gases like methane and ethane can reveal key details about distant Kuiper Belt objects.

Pluto isn’t the only dwarf planet in our solar system's outer reaches. Now is an ideal time to look for the egg-shaped Haumea ...