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Gan De was an ancient Chinese astronomer born in the State of Qi. Along with Shi Shen, he is believed to be the first   1． history known by name to produce a star catalogue (星表). He made fairly 2． (detail) observations of the five major planets during the 3． (four) century.

Gan De may have been the first to describe one of the 4． (satellite) of Jupiter (木星), usually invisible without the aid of telescopes. He gave the following 5． (describe) of Jupiter’s journey: Every 12 years Jupiter returns to 6． same position in the sky; every 370 days it disappears in the fire of the Sun in the evening to the west, 30 days later it reappears in the morning to the east... In 1981, Gan’s work 7． (identify) by Xi Zezong as describing a naked-eye observation of either of the two 8． (large) and brightest satellites in summer 365 BC.

Gan was one of the earliest practitioners of Chinese astronomy. As the earliest attempt 9． (document) the sky during the Warring States period, Gan De’s work possesses high scientific value. He wrote two books, the Suixing Jing and the Tianwen Xingzhan, 10． sadly both texts have been lost. Some of his works’ titles and fragments (片段) quoted from them are known from later texts.