Clyde William Tombaugh (; February 4, 1906 – January 17, 1997) was an American astronomer and telescope maker, best known for discovering Pluto in 1930, marking the first detection of what would eventually be recognized as the Kuiper belt. At the time, Pluto was referred to as the ninth planet in the Solar System, a classification that stood for over seven decades.
Born in Illinois, and raised on farms in Kansas, Tombaugh was largely self-taught in astronomy and optical engineering, building his own telescopes from spare parts and grinding lenses by hand. His skill and determination led to a position at Lowell Observatory in Flagstaff, Arizona, where he conducted photographic surveys of the night sky. In addition to Pluto, Tombaugh identified hundreds of asteroids and a variety of star clusters, galaxies, and variable stars, thereby contributing significantly to the cataloguing of the night sky.
As a professor at New Mexico State University, he led the Planetary Patrol project, which helped determine Mercury's rotation period, monitored Jupiter's Great Red Spot, and developed new photographic techniques for satellite searches.
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