BRAHE, TYCHO (1546-1601), Danish astronomer, was born on Dec. 14, 1546, at the family seat of Knudstrup in Scania, then a Danish province. He studied at Copenhagen, Leipzig, Rostock and Augsburg, and in 1571 was permitted by his mater nal uncle, Steno Belle, to install a laboratory at his castle of Herritzvad, near Knudstrup; and there, on Nov. ii. 1572, he caught sight of the famous "new star" in Cassiopeia. His observa tions were published as De Nova Stella (Copenhagen, 1J73, fac simile reprint I901).
Tycho's marriage with a peasant-girl in 1573 somewhat strained his family relations. He delivered lectures in Copenhagen by royal command in 1574 ; and in 1575 travelled through Germany to Venice. Frederick II., king of Denmark, bestowed upon him for life the island of Hveen in the Sound, together with a pension of 500 thalers, a canonry in the cathedral of Roskilde, and the income of an estate in Norway. The first stone of the magnificent observatory of Uraniborg was laid on Aug. 8, 1576; it was the scene, during 21 years, of Tycho's labours. Frederick's successor, Christian IV., was less tolerant of Tycho's arrogance. His pension and fief having been withdrawn, he sailed for Rostock in June He spent the following winter at Wittenberg, and reached Prague in June 1599, well assured of favour and protection from the emperor Rudolph II., who assigned him the castle of Benatky for his residence, with a pension of 3,00o florins; his great instru ments were moved thither from Hveen, and Johannes Kepler joined him in Jan. 160o. Tycho died at Benatky on Oct. 24, 1601.
Tycho's principal work, entitled Astronomiae instauratae pro gymnasrnata (2 vols., Prague, 1602-03) was edited by Kepler. The first volume treated of the motions of the sun and moon, and gave the places of 777 fixed stars (this number was increased to 1,005 by Kepler in 1627 in the "Rudolphine Tables") . The sec ond, which had been privately printed at Uraniborg in 1588 with the heading De mundi aetherei recentioribus, phaenomenis, was mainly concerned with the comet of 1577, demonstrated by Tycho from its insensible parallax to be no terrestrial exhalation, as commonly supposed, but a body traversing planetary space. It included, besides, an account of the Tychonic plan of the cosmos, in which a via media was sought between the Ptolemaic and Copernican systems. The earth retained its immobility ; but the five planets were made to revolve round the sun, which, with its entire cortege, annually circuited the earth, the sphere of the fixed stars performing meanwhile, as of old, its all-inclusive diurnal rotation (see ASTRONOMY : History) . Under the heading Astronomiae instauratae mechanica, Tycho published at Wands beck, in a description of his instruments, together with an autobiographical account of his career and discoveries, including the memorable one of the moon's "variation" (see MooN) . His Epistolae Astronornicae, printed at Uraniborg in 1596, were em bodied in a complete edition of his works issued at Frankfurt in 1648. He constructed a table of refractions, allowed for instru mental inaccuracies, and eliminated by averaging accidental errors. He, moreover, corrected the received value of nearly every astro nomical quantity.
See J. L. E. Dreyer, Tycho Brahe (189o) , which gives full and authentic information regarding his life and work. Also Gassendi, Vita (Paris, 16S4) ; Lebensbeschreibung, collected from various Danish sources, and translated into German by Philander von der Weistritz (Copenhagen and Leipzig, 1756) ; F. R. Friis, Tyge Brahe (Copen hagen, 1871) ; R. A. Gray, "The Life and Work of Tycho Brahe," Roy. Astron. Soc. of Canada, Journ. xvii. (1923).