Jupiter has 79 known moons, almost making it a solar system by itself. In January 1610, Italian astronomer Galileo Galilei discovered four of Jupiter’s moons which are now called lo, Europa, Ganymede and Callisto. Originally, Galileo referred to them numerically as I, II, III, and IV. The first moon he discovered was lo and it is closest to Jupiter among the four. He published his observations in a book called The Starry Messenger. However, Simon Marius, who discovered the moons independently around the same time as Galileo, gave these moons their present names.
Galileo’s discovery proved the importance of the telescope as a tool for astronomers. It made possible for humans to perceive celestial objects that remained unseen by the naked eye.
Galileo’s discovery was a turning point in astronomical history as it put an end to the geo-centric model of the universe.
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