[ Autographs ] CLYDE W. TOMBAUGH American astronomer and the discoverer of Pluto. S.P. 10in x 8in, a color NASA photograph of an artist's rendering of Pluto and its moon sign along the top margin with the caption in his hand: "Discover of the 9th Planet, Pluto Clyde W. Tombaugh, Feb 18, 1930". Very good.