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The search for Planet X The search for Pluto did not begin with Clyde Tombaugh, to be fair. That distinction belongs to the visionary astronomer Percival Lowell. In 1894, Lowell founded Lowell ...

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 ...

(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 ...

Pluto sits far out in the Solar System, small and dim, moving at a pace that barely fits human timelines. It was found in ...

For the first time since Pluto was demoted, the idea of a true ninth planet is edging from speculation toward something testable. Instead of restoring Pluto, researchers are closing in on a different, ...

Pluto was relegated to the catalog of minor planets, a major planet no more. Still, astronomers admitted that they knew very little about Pluto, which many believed was nothing more than a very cold, ...

Nine years, 3 billion miles, and $700 million later, we are finally getting the very first high resolution photos of Pluto, thanks to a NASA spacecraft called New Horizons. It’s a pretty small planet ...

Pluto, discovered 90 years ago on Feb. 18, 1930, was long considered the solar system's ninth planet. Although small, it orbits the sun and has the spherical shape required to be considered a planet.