415 years ago, Galileo Galilei pointed his telescope at celestial objects for the first time.

For the first time, humans observed the Moon's features: its craters and more. And when he pointed the telescope at Jupiter, he saw four "stars" next to it. He thought of them as "Galilean satellites," and thus they were named. This is how Ganymede, Callisto, Europa, and Io were discovered.

📸 Luis Argerich