The sidereal messenger of Galileo Galilei : $b and a part of the preface to Kepler's Dioptrics containing the original account of Galileo's astronomical discoveries

"The Sidereal Messenger of Galileo Galilei" is an astronomical treatise published in 1610. It marks the first published scientific work based on telescopic observations. Galileo reveals stunning discoveries: mountains on the Moon's surface, hundreds of previously invisible stars in the Milky Way, and four celestial bodies orbiting Jupiter. Through detailed drawings and descriptions, he challenges long-held beliefs about the heavens. His observations of what he called the "Medicean Stars" would forever change humanity's understanding of the cosmos and our place within it. (This is an automatically generated summary.)