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The search for Planet X continued at the Lowell Observatory. In 1929 a young astronomer called Clyde Tombaugh [pictured] started work there after having impressed them with drawings of his observations of Jupiter and Mars. He undertook a systematic review of photographs taken using a 13-inch astrograph. He used blink comparator to flick between photographs taken at different times in order to spot any moving objects. On 18th February 1930 Tombaugh noticed the sort of moving object that he was looking for when he compared two pictures taken on the 23rd and 29th of January. Subsequent observations confirmed that he had found a large stellar body orbiting the Sun.