By means of the telescope Galileo (1564-1642) discovered the existence of a quantity of stars much greater than those observable to the naked eye. In his Sidereus Nuncius [The Starry Messenger] he included two engravings: one of the zone of Orion's belt and sword, which, in addition to the stars already known, showed 80 new ones; the other of the Pleiades, with 30 stars invisible to the naked eye.
For centuries philosophers had hotly debated the true nature of the Milky Way, which Galileo revealed with the force of "reasoned experimentation". Thanks to the telescope, in fact, he demonstrated that it is a mass of innumerable stars, which cannot be individually distinguished by the naked eye.