The Medici family played an important role in Galileo’s life. Galileo was the son of a poor descendent of a Florentine noble family. He wanted to become a painter but his father felt that painting was not a worthy profession for a man of noble birth. So Galileo studied medicine. He began his career in 1589 as a teacher of mathematics in the University of Pisa. His colleagues were unable to bear his sarcasm and independence, and they made it clear to him that if he decided to resign, they would gladly accept his resignation.
In 1592, Galileo moved to the University of Padua where he taught geometry, mechanics, and astronomy for eighteen years. Cosimo II de' Medici, Grand Duke of Tuscany, who had once been Galileo’s student, invited him to Florence where he could do his studies and experiments in a rich environment without having to worry about the interference from his detractors. Galileo accepted the offer and he spent the final years of his life under the protection of the Medici. Cosimo gave Galileo the title of court mathematician. This position brought Galileo the freedom to present his radical ideas in astronomy and mathematics. He made a powerful case to support the theories of Nicolaus Copernicus.
In his 1610 book Sidereus Nuncius, Galileo honored his Medici benefactors by naming the four moons of Jupiter, which he had discovered through his telescope, Medicea Sidera (Medicean stars), in reference to Cosimo and his three brothers.