Clyde Tombaugh

Clyde William Tombaugh was born on February 4, 1906, in Streator, Illinois, and grew up on farms in Kansas. Largely self-taught in astronomy and optical engineering, he built his own telescopes from spare parts and hand-ground lenses. His interest in astronomy was sparked at age twelve after visiting Yerkes Observatory, and was further encouraged by an uncle who was an amateur astronomer. Financial hardship forced Tombaugh to leave high school for a year to help his family with crops, and later a hailstorm in 1928 destroyed his family’s farm crops, ending his hopes of attending college. Undeterred, he constructed several telescopes beginning in 1926, digging a pit to test his mirrors in stable air. He sent drawings of Jupiter and Mars to Lowell Observatory in Flagstaff, Arizona, which led to a job offer there in 1929. At Lowell, Tombaugh was tasked with a systematic photographic search for a trans-Neptunian planet, or Planet X, predicted by Percival Lowell. Using the observatory’s astrograph, he took images of the same sky sections on different nights and compared them with a blink comparator. On February 18, 1930, he spotted a moving object on plates taken the previous month. This object, later named Pluto, was initially considered the ninth planet. The name Pluto was proposed by an eleven-year-old English girl, Venetia Burney, and was officially adopted on May 1, 1930. Following the discovery, Tombaugh earned bachelor’s and master’s degrees in astronomy from the University of Kansas in 1936 and 1938. He continued searching for other trans-Neptunian objects for years, finding none, which led him to conclude Pluto was a planet. Beyond Pluto, he identified hundreds of asteroids, star clusters, galaxies, and variable stars. Later, 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. After retiring in 1973, he continued building telescopes and advocated for the study of unidentified flying objects.