Galileo's observations of stars in Orion. Sketches of stars made from telescope observations by the Italian physicist, mathematician and astronomer Galileo Galilei (1564-1642). The known naked-eye stars (in the belt and sword region of the constellation of Orion) are shown as larger than the new stars Galileo observed with his telescope. These pioneering observations were first made in 1610, using the telescopes that Galileo had built in 1608. Galileo's also observed the Moon, and the planets, including the larger satellites of Jupiter. His observations challenged the existing worldview that said the heavens were perfect and unchanging. This page is from the 1610 edition of 'Sidereus Nuncius'.