Weitekamp, Margaret A., DeVorkin, David H., and Kidd, Diane. 2013. Pluto's Secret: An Icy World's Tale of Discovery. New York: Abrams Books for Young Readers.
On Feb. 18, 1930, 24-year-old Clyde Tombaugh discovered a faint, remote object on photographic plates he had taken Jan. 23 and Jan. 29 from Lowell Observatory in Flagstaff, Ariz. Astronomers credited ...
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