Once the quirky underdog of our solar system, Pluto held planetary status until 2006, when it got a cosmic demotion that still stings space fans. Discovered in 1930, Pluto was the ninth planet for ...

Pluto's days, though they drag on a bit at around 153 hours, are nothing compared to its years. Pluto's orbit takes 248 Earth ...

Pluto's discovery was widely celebrated, especially in the U.S. After all, it was the first planet discovered in the new world, and America needed the win in 1930. "I think because it was discovered ...

Earth has a newly-discovered neighbor in the solar system. But the heavenly body – possibly a dwarf planet à la Pluto – isn't a frequent visitor. Located beyond Neptune, its extreme orbit ...

Scientists who argue for Pluto to be classified as a planet are getting more ammo for a debate that has raged over the last 15 years. A team of researchers published a study in the scientific journal ...

(Correction: An earlier version of this story misstated how far Pluto is from the sun. The correct number is 3.7 billion miles.) What was discovered in Flagstaff, Arizona, and killed off in Prague? If ...

For the first time since Pluto was demoted, the idea of a true ninth planet is edging from speculation toward something ...

Pluto, discovered in 1930, was once considered the ninth planet in our solar system. In 2006, the International Astronomical Union reclassified Pluto as a dwarf planet because it doesn't meet all the ...

Pluto may be a “dwarf” planet, but it is still a planet. In 2006, the International Astronomical Union, responding to the discovery of several Pluto-like objects in the Kuiper Belt beyond Neptune, ...