1564-1642. Italian astronomer and physicist. The first to use a telescope to study the stars. Discoverer of the first moons of an extraterrestrial body (see above). Galileo was an outspoken supporter of Copernicus's heliocentric theory. In reaction to Galileo, the Church declared it heresy to teach that the Earth moved and imprisoned him. The Church clung to this position for 350 years; Galileo was formally exonerated in 1992.