415 Years Ago: Astronomer Galileo Discovers Jupiter’s Moons

On Jan. 7, 1610, Italian astronomer Galileo Galilei peered through his newly improved 20-power homemade telescope at the planet Jupiter. He noticed three other points of light near the planet, at first believing them to be distant stars. Observing them over several nights, he noted that they appeared to move in the wrong direction with […]

Published by NASA on 01/08/2025

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