Pluto Discovery Plate

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Pluto was discovered by Clyde Tombaugh of the Lowell Observatory by comparing this photographic plate taken on the night of January 23, 1930 with two others taken in the same month. Because Pluto is so small and so distant from the Sun, the image of the planet is extremely faint and difficult to see. The original plate on display in the Exploring the Planets gallery in the National Air and Space Museum in Washington, DC.