Gan De

Gan De may have been the first to describe one of the Galilean moons of Jupiter, usually invisible without the aid of telescopes. In the 20th century, a fragment of Gan's work, in a later compilation of astronomical texts, was identified by Xi Zezong as describing a naked-eye observation of either of the two largest and brightest moons, Ganymede or Callisto in summer 365 BC.

Life

Gan was one of the earliest practitioners of Chinese astronomy. As the earliest attempt to document the sky during the Warring States period, Gan De's work possesses high scientific value. He wrote two books, the Treatise on Jupiter and the 8-volume Treatise on Astronomical Astrology. Gan De also wrote the Astronomic Star Observation (天文星占, Tianwen xingzhan).

Shen and Gan together made fairly detailed observations of the five major planets during the 4th century. Gan De made some of the first detailed observations of Jupiter in recorded history.