Brahe, Tycho (1546–1601)

A Danish astronomer, Tycho Brahe was born into a noble and wealthy family, the son of a minister to the king of Denmark. He studied at the University of Copenhagen, where he prepared for a career in law. On August 21, 1560, however, he witnessed an eclipse of the sun. Observation and mathematical calculations had already predicted the eclipse, an achievement that inspired Brahe to pursue astronomy. Discouraged by the conflicts and disagreements in astronomical measurements, he set out to collect as much information as possible from a single observation point with the most accurate instruments available, and develop a more consistent and accurate system of astronomical observation.

Brahe built an observatory known as the Uraniborg on the island of Hven. There he developed his own model of the universe, the Tychonic system, which reconciled the conflicts in the old Ptolemaic (earth-centered) and new Copernican (heliocentric) systems. In 1572 he observed a suddenly bright star in the constellation Cassiopeia, and described his findings in De Stella Nova, which coined the term “supernova.” This observation was important for its revolutionary concept that the heavens were not fixed and eternal, as in the traditional view. Tycho believed in a geocentric universe, in which the earth was fixed, the sun orbited the earth, and the planets orbited the sun. He believed that if the earth did move, then nearer stars should shift with respect to background stars; this “parallax shift” was indeed present but not visible at the time. (Brahe was the last major astronomer to work by the naked eye, without using a telescope.)

At odds with the king of Denmark over his theories, Brahe moved to Prague in 1597 and won the patronage of Emperor Rudolf II, who used him as a court astrologer. Brahe jealously guarded his astronomical measurements; after his death by unknown causes they fell into the hands of his assistant, Johannes Kepler. The circumstances of Brahe's demise have led some historians to conclude that Kepler murdered his employer out of professional jealousy. Whatever the truth of the matter, in the following years Kepler relied on Brahe's calculations to develop a set of new laws governing the motion of the planets.

See Also: Copernicus, Nicolaus; Galilei, Galileo; Kepler, Johannes