In 1610, Galileo Galilei released Sidereus Nuncius (or Starry Messenger), a short treatise that outlined a series of discoveries made possible by his newly invented telescope. Galileo’s telescope revealed the mountains and craters scattered across the surface of the moon, four celestial bodies (now known to be moons) orbiting Jupiter, and an array of stars stretching across the sky. This challenged received wisdom about the structure and composition of the universe, laying the foundation for increasingly radical transformations that would soon follow—chiefly, the transition from a geocentric model of the universe to the concept of a heliocentric solar system. This is the second edition of Sidereus Nuncius, printed in Frankfurt the same year as the first edition in Venice.