tombaugh, clyde william

Science Dictionary
Tombaugh   (tŏm'bô')  Pronunciation Key 
American astronomer who discovered the planet Pluto in 1930. The existence of an outermost planet, known as Planet X, had been predicted some years earlier by the American astronomer Percival Lowell based on apparent perturbations in the orbits of Neptune and Uranus. Tombaugh's careful analysis of celestial photographs did reveal a new planetary body, although it was too small to have caused the perturbations. Planet X itself was never found.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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tombaugh, clyde william

American astronomer who discovered Pluto in 1930 after a systematic search for a ninth planet instigated by the predictions of other astronomers. He also discovered several clusters of stars and galaxies, studied the apparent distribution of extragalactic nebulae, and made observations of the surfaces of Mars, Venus, Jupiter, Saturn, and the Moon

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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