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 ...

February 18 marks the discovery of Pluto by astronomer Clyde W. Tombaugh. The discovery reshaped the understanding of the solar system, as Pluto was long considered ...

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 ...

Pluto was considered the ninth planet for 76 years after its discovery in 1930. Then in 2006, the International Astronomical ...

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

For many people, the definition of a planet was only made clear in 2006, when the spunky world Pluto was demoted from a planet to a dwarf planet. Now, a team of astronomers is pushing for “planet” ...

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