Tyeho Or Tyge De Brahe, a Danish astronomer, of Swedish origin, born at Knudstorp, in Scania, which then belonged to Denmark, Dec. 4, 1546, died in Prague, Oct. 13, 1601. He came of an ancient princely family, the ruins of whose castle, Wisingsborg, are still visible on the shore of Lake Wetter. He was the second of ten children, and he as well as his youngest sister Sophia early displayed great intellectual ability. After having been under the care of private tutors, his maternal uncle, Steno Belle, sent him after the death of his father to Copenhagen to study philosophy, and in 1562 to Leipsic to study law; but astronomy engrossed his attention almost exclusively, the fulfilment of the prediction in regard to the eclipse of the sun in 1560 having essentially contributed to strengthen his faith in that science. His relatives insisting upon his preparing himself for the law and for statesmanship, he clandestinely devoted the night to astronomical observations, with the aid of a small celestial globe and a wooden circle for the measurement of the stars, thus observing in 1563 the junction of Saturn with Jupiter. The inheritance of a considerable fortune in 1565 left him at liberty to prosecute his experiments, in which he was encouraged by the Danish government in 1568. After spending some time in Augsburg, he returned to Copenhagen in 1570 with a European reputation, which was increased in 1572 by his discovery of a new star, though this did not reappear after 1574. His uncle gave him every opportunity for astronomical observations at his seat near Knudstorp; but his marriage with a peasant girl produced great unpleasantness with his relatives, though Frederick II. of Denmark endeavored to effect a reconciliation.

At the king's request he lectured at Copenhagen in 1574 on the theory of comets and on mathematics, and he afterward visited Germany, Switzerland, and Italy. He resolved in 1576 to settle permanently in Basel; but the king secured his services by bestowing upon him for life the island of Hven in the Sound, and by building there for him a laboratory and a magnificent observatory, which was finished in 1580. It acquired great celebrity under the name of Uranienborg, and Brahe gave here such a powerful impetus to astronomical science, that distinguished personages of all countries visited him, including James VI. of Scotland, afterward James I. of England, while in Denmark to marry the princess Anne. Frederick II. spared no effort and no money to enlarge the scope of the astronomer's labors, and gave him a pension of 2,000 crowns and the canonry of Roeskilde with a revenue of 1,000 crowns, besides other endowments. But soon after the king's death he lost all these advantages, owing to the hostility of Walchendorff and other members of the council of regency. Not only was he driven from Uranienborg on account of his inability to defray the expenses of the observatory, but he was also obliged to leave Copenhagen; and in 1597 he abandoned Denmark for ever.

He went with his family to Rostock, and then to Holstein, where he prevailed upon Heinrich von Rantzau to recommend him to Rudolph II. of Germany. This emperor received him with great distinction, and assigned him in 1599 a pension of 3,000 florins in gold and a residence in his own chateau of Benach, near Prague, where Kepler visited him in 1600. Subsequently Brahe was installed by the emperor in an extensive mansion in Prague, which he proposed to convert into another Uranienborg, but he died too soon for the accomplishment of this purpose. He was interred in the Theinkirche, one of the principal churches of Prague, where a marble effigy perpetuates his memory. The emperor purchased his valuable collection of instruments, but, with the exception of one sextant, they have all been destroyed in times of war; and his famous celestial globe of brass, said to have cost 5,000 thalers, found its way back to Copenhagen after many vicissitudes, only to be burnt during the conflagration of the palace in' 1720. Brahe was of a violent and hasty temper, and so superstitious that he kept about him a lunatic whose ravings he regarded as prophetic. - His system was not extensively adopted, and is considered as but a modified form of that of Ptolemy. But to Brahe belongs the merit of having been the first to lay the foundation of practical astronomy, and Kepler used his numerous and for his time wonderful observations effectively in his discoveries.

Brahe's principal publications include Calendarium Naturale Magicum (1582), Progymnasmata Astronomica (2 vols., 1587-'9), Astronomicae instauratce Mechanica (a description of his instruments, 1598), and Epistolm As-tronomiccB (1610). His observations were collected by his disciples in 1666 (Historia Ca-lestis, 20 vols.). His chief biographers are, in Italian, Gassendi (Paris, 1655); in German, Helfrecht (Hof, 1798); and in Danish, Peder-sen (Copenhagen, 1838). See also Brewster, "Martyrs of Science" (London, 1841), and Bertrand, Les fondateurs de Vastronomie mo-derne (Paris, 1865).