Satellites of Jupiter

Galileo also discovered four satellites revolving around Jupiter, printing more than 60 observations of their positions from night to night. (Figure 1) (Figure 2) (Figure 3) (Figure 4) (Figure 5)

The satellites of Jupiter proved that multiple centers of revolution exist in the solar system. These satellites removed an anomaly in the Copernican system, for why should the Earth have its own Moon unlike any of the other planets? The satellites also proved, contrary to the argument of the Aristotelian physicists, that a moving planet would not leave its Moon behind. Jupiter was a miniature Copernican system set in the sky to persuade Catholics not to abandon their own astronomer.

“We have moreover an excellent and splendid argument for taking away the scruples of those who, while tolerating with equanimity the revolution of planets around the Sun in the Copernican system, are so disturbed by the attendance of one Moon around the Earth while the two together complete the annual orb around the Sun that they conclude that this constitution of the universe is impossible. For ... our vision offers us four stars wandering around Jupiter like the Moon around the Earth.” Galileo, Sidereus Nuncius, trans. Albert Van Helden (University of Chicago, 1989).

Exhibit credit: Kerry Magruder, with the assistance of , Marilyn B. Ogilvie, Duane H. D. Roller.