Pluto Discovered

18 Feb 1930. Pluto has yet to complete a full orbit of the Sun since its discovery, as one Plutonian year is 247.68 years long.[22

23-year-old Clyde Tombaugh, who had just arrived at the Lowell observatory was tasked to systematically image the night sky in pairs of photographs, then examine each pair and determine whether any objects had shifted position. Using a blink comparator, he rapidly shifted back and forth between views of each of the plates to create the illusion of movement of any objects that had changed position or appearance between photographs. On February 18, 1930, after nearly a year of searching, Tombaugh discovered a possible moving object on photographic plates taken on January 23 and 29. A lesser-quality photograph taken on January 21 helped confirm the movement.[21] After the observatory obtained further confirmatory photographs, news of the discovery was telegraphed to the Harvard College Observatory on March 13, 1930.[17]

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