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Clyde Tombaugh

discoverer of Pluto

Clyde Tombaugh

Clyde William Tombaugh was born on a farm near Streator, Illinois, on February 4, 1906. His family moved to a farm near Burdett, Kansas, in 1922, and he graduated from Burdett High School in 1925.

The first telescope Clyde ever looked through was provided by his uncle, and the first one he owned was bought from Sears. In 1925, he decided to build his own telescope, and his father took a second job to pay for the materials. It would be but the first of the more than thirty telescopes he would build over the course of his lifetime. In 1928, Tombaugh completed construction of a very accurate 23-centimeter reflecting telescope, which he built using a variety of spare parts (including part of a crankshaft from a 1910 Buick). He subsequently used this telescope to observe the planets Jupiter and Mars. He then sent very detailed drawings of his observations to the Lowell Observatory (near Flagstaff, Arizona), asking for comments and suggestions. He got his comments, as well as an offer to join the observatory staff as a junior astronomer. He gladly accepted the job, and arrived at Lowell on January 15, 1929.

Clyde with one of his home-made telescopes
Clyde with one of his home-made telescopes

Tombaugh's job at Lowell was to help search for "Planet X," a planet Percival Lowell (the observatory's founder) believed lay beyond the orbit of Neptune. Using a 13-inch astrograph, Tombaugh had to photograph one small piece of the night sky at a time, then photograph that same small piece again a few nights apart. He then placed the photographic plates into a device called a blink comparator that "blinked" back and forth between the two plates at a speed fast enough to make the two appear as one; any object that moved between the frames would be the elusive planet. After ten months of intensive and uncomfortable work, Tombaugh had managed to photograph and study 65% of the night sky. The work paid off, however, for on February 18, 1930, while studying images taken the previous January, Tombaugh spotted an object that had changed positions between one exposure and the next. On March 13, 1930, the Lowell Observatory announced that a new planet had been discovered orbiting beyond Neptune; that planet was subsequently named Pluto.

the astrograph Tombaugh used
the astrograph Tombaugh used

As a result of his discovery, Tombaugh was given a scholarship to the University of Kansas, from which he earned his Bachelor's (1936) and Master's (1939) degrees. He then returned to Lowell, and remained there until 1945. He began teaching at New Mexico State University in 1955, and was a professor there from 1965 until his retirement in 1973.

The discovery of a planet made his career, but Tombaugh's record of discovery did not end there. He went on to discover several galactic clusters, fourteen named asteroids, a comet, a cluster of 1,800 galaxies, and much more. Out of the Darkness: The Planet Pluto, his telling of the search and discovery of Pluto, was co-written with Patrick Moore and published in 1980.

Clyde W. Tombaugh died in Las Cruces, New Mexico, on January 17, 1997.

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This page was last updated on 08/19/2018.