Pluto: The Discovery of a Planet

To mark the 75th anniversary of the discovery of the planet Pluto, The Planetary Society presents to its readers the remarkable story of the discovery.

Read here how Clyde Tombaugh, a farm boy from Kansas with a high school education, succeeded where accomplished professional astronomers had failed, and discovered the elusive 9th planet. Learn about how the closed cosmos of the ancients became the open universe of modern times, opening the door to new discoveries in the heavens. Find out about William Herschell's discovery of Uranus, and how the detection of Neptune turned into nationalist feud between England and France. Meet Percival Lowell, the eccentric American visionary who believed in intelligent life on Mars and launched the search for "Planet X."

All this and more on our 75th anniversary special:

PLUTO: DISCOVERY OF A PLANET

Part 1: The Blinking Image

Part 2: Out of the Six-Planet World

Part 3: Planet X

Part 4: Clyde's Search

Part 5: The Aftermath

Part 6: From Pluto to Sedna