On February 4, 1906 (January 11, 1906), Clay Tombaugh, the discoverer of Pluto, was born. In 1929, the Lover Observatory chief invited Tombaugh to join the search line for the unknown planet. They searched the sky, photographed a lot of images, and carefully examined each image, working hard and boring. On January 21, 1930, Tombaugh finally discovered the new planet in the Gemini Observatory. Pluto was the latest planet to be discovered, and since the day it was discovered more than 70 years ago, Pluto and the "controversial" word were linked together, because the process of its discovery was based on a mistake; on January 21, 1930, Tombaugh was found due to the initial calculation of its mass, and it was mistakenly included in the planets of the Universe. In 1930,