Galileo Galilei (1564-1642), Italian astronomer and physicist. This portrait is from the front of his 1613 book on sunspots ('Macchie Solari'). The Italian inscription describes Galileo as a member of the Lyncean Academy (founded 1603), and that he is the philosopher and mathematician of the Grand Duke of Tuscany. Galileo was appointed to this position in 1610. This was the same year that he made one of his most famous discoveries, using his telescope to discover the four largest moons of Jupiter. When he observed sunspots a few years later, Galileo correctly argued that they were on or near the Sun's surface.