On February 18, 1930, the American astronomer Clyde Tombaugh discovered Pluto! Before he discovered Pluto, another astronomer ...

What was discovered in Flagstaff, Arizona, and killed off in Prague? If you answered "Pluto's planethood," your grasp of the astronomical is excellent. Feb. 18 marks the 95th anniversary of the ...

Pluto's discovery by Clyde Tombaugh, key political changes in Scandinavia and America, plus cultural and scientific milestones.

It would be understandable if you stopped thinking as much about Pluto after it was “demoted” from being considered one of the nine planets sharing the Earth’s solar system to being classified as a ...

Everyone's favorite dwarf planet, Pluto, was discovered just 95 years ago. Here's the story of how the once-ninth planet was discovered. In the early 20th century, the businessman, astronomer, and ...

From 1905 until his death in 1916, Percival Lowell searched for a ninth planet, which he called Planet X. Lowell had predicted the planet based on irregularities in the orbit of Uranus. In 1929, ...

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 ...

FLAGSTAFF, Ariz. It's been 75 years since the discovery of Pluto, but it remains a mystery. Perhaps in another 10 years some of its secrets will be revealed when a space probe gets close enough for a ...

We classified Pluto before really understanding it—just like we reduce people to job titles or put names on relationships ...

Clyde Tombaugh noticed a speck of light that was Pluto in 1930. — -- Clyde Tombaugh is finally getting to visit the speck of light he spotted at the edge of the solar system in 1930. New Horizons ...

(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 ...