Utah Skies: Clyde Tombaugh and Pluto

Feb 23, 2021

Credit Dell Vance

Clyde Tombaugh, as a young man, built his own Telescopes and made sketches of Mars and Jupiter. In 1929 he sent his sketches to the Lowell Observatory in Flagstaff, Arizona. The staff was impressed with his work and offered him a job as a researcher on a project to find Planet X.

The staff had calculated where Planet X should be. Each night Clyde would systematically photograph several slices of that section with a special telescope called an astrograph. He would then return to that same area several nights later and retake the photographs. The photos were processed and then compared to see if any of the stars in that section had moved. If so, they would know that they had the visual proof of Planet X. 

After 10 months, on February 18, 1930, he was successful in identifying Planet X. The planet was eventually named Pluto. For 76 years it was categorized as a planet. In 2006 it was recategorized, primarily due to its size and orbit, as a Dwarf Planet. Pluto is over 3 billion miles from earth.

With modern computerized telescopes, amateur astronomers can duplicate Clyde’s process. In most telescopes, Pluto will appear as a very dim object and not easily recognized among the stars. Therefore, images can be taken and compared just like Clyde did.

Clyde Tombaugh graduated from college 6 years after his great discovery of Pluto with a Bachelor of Science degree in 1936 and a Master of Science degree in 1938. His contribution to Astronomy for finding Pluto, is not that he found a planet, but that it was the first object identified in the Kuiper belt. 

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