Persistence paid off for American astronomer Clyde Tombaugh, who discovered the planet Pluto. After astronomers calculated a probable orbit for this “suspected” heavenly body, Tombaugh took up the search in March, 1929. Time magazine recorded the investigation: “He examined scores of telescopic photographs each showing tens of thousands of star images in pairs under the dual microscope. It often took three days to scan a single pair. It was exhausting, eye-cracking work, in his own words, “brutal, tediousness.” And it went on for months. Star by star, he examined 20 million images. Then on February 18, 1930, as he was blinking at a pair of photographs in the constellation Gemini, “I suddenly came upon the image of Pluto!” It was the most dramatic astronomic discovery in nearly 100 years.