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Tycho BraheTycho Brahe

[tI' kO brah hE'] doubter of the Ptolemaic structure of the universe

Tycho Brahe was born in Skane (then in Denmark, now in Sweden) on December 14, 1546, the eldest of two sons and one daughter born to Otto and Beatte (Bille) Brahe, both of whom were from noble Danish families. As per a family agreement, Tycho was adopted by his paternal uncle, J÷rgen Brahe, who, in April of 1559, sent him to study philosophy and rhetoric at the University of Copenhagen. Tycho's studies were interrupted by the occurrence of a predicted total solar eclipse on August 21, 1560, however, and from that time on he was much more interested in astronomy than philosophy.

Brahe's quadrant at AugsburgSent to study law at the University of Leipzig in 1562, Brahe secretly studied astronomy instead and began continuous observations with a globe, a pair of compasses and a "cross-staff." He quit Leipzig on May 17, 1565, but, after the death of his uncle the next month, went on to the universities of Wittenberg and then Rostock. At Rostock, a dispute with a fellow student over a mathematical equation led to a sword duel, which in turn led to Brahe losing the tip of his nose; from that time on he wore a metal prosthesis that has been variously described as being made of either copper, bronze, gold, or some other metal. He finished his studies at the University of Augsburg, where he built a huge quadrant that permitted he and his fellow students to make extremely precise observations of heavenly bodies. Matriculating from Augsburg in 1569, Brahe once again embarked on a "study tour" of Germany, this time with a focus on chemistry.

Right: Brahe's quadrant at Augsburg.

Brahe's depiction of the 'new star' he observedBrahe ended his "study tour" and returned to the family estate toward the end of 1570 after learning that his father was seriously ill. After his father died on May 9, 1571, he was "taken in" by his maternal uncle, Sterno Belle, who allowed Tycho to build an observatory at his castle near Knudstrup. There, on November 11, 1572, he observed a new star in the constellation Cassiopeia; he published De Nova et Nullius Aevi Memoria Prius Visa Stella (On the New and Never Previously Seen Star) the following year. [Astronomers now know that Brahe actually observed a supernova, the spectacular explosion of an old star, not the birth of a new star.]

Left: Brahe's depiction of the 'new star' he observed.

In 1573, Brahe became romantically involved with Kirsten J°rgensdatter, a peasant girl. Although the two never formally married, they lived together as husband and wife until his death. The couple eventually had eight children, six of whom lived into adulthood. In 1574, they moved to Copenhagen, where Brahe spent a year giving a course of lectures at the university.

drawing of UraniborgAfter another "study tour" of Germany in 1575, Brahe accepted an offer from King Frederick II of Denmark to establish an observatory on the island of Hveen in the sound between Denmark and Norway. Built between 1576 and 1580, Uraniborg was the first building ever designed specifically for astronomical observations. Brahe personally designed and built many of the observatory's instruments, took great pains to calibrate them, and instituted regular nightly observations of the heavens. He also ran his own printing press, from which he published De Mundi Aetherei Recentioribus Phaenomenis (Concerning the New Phenomena in the Ethereal World) in 1588. This work not only contained details about a comet he observed in 1577, but also included his "plan of the cosmos."

Right: Drawing of Uraniborg.

Brahe's depiction of the universeIn Brahe's time, astronomers generally accepted a theory formulated by Ptolemy 1,400 years earlier -- that the Earth was the center of the universe, and had no motion. Brahe's attention to detail in his observations of the 1572 star, 1577 comet, and of planetary orbits led him to easily dismiss the Ptolemaic system, but he also rejected the Heliocentric Theory (sun-centered universe) of Nicolas Copernicus. Brahe's "compromise theory" still placed the Earth at the center of the universe, with the Sun, Moon, and stars revolving about it, but had all of the other known planets revolving about the Sun, with the comet he had discovered in 1577 following a circular path between the orbits of Venus and Mars.

Left: Brahe's depiction of the universe.

In 1597, a dispute with King Christian IV, who had succeeded Frederick II in 1588, led Brahe to pack up his books and instruments and leave Denmark. After spending a couple of years in Germany, he settled in Prague as Imperial Mathematician in the court of Holy Roman Emperor Rudolph II. One of the young astronomers who worked under Brahe in Prague was Johannes Kepler, whose later discovery that planets move in elliptical orbits was spurred by Brahe's insistence on observing the Moon and planets throughout their orbits, not just at important points (apogee, perigee, etc.).

Tycho Brahe contracted a urinary infection and died unexpectedly on October 24, 1601, and was buried at Tyn Church in Prague.

Although Brahe's "compromise theory" of the universe was not universally accepted, he was still well respected by his contemporaries. The first astronomer to make corrections for atmospheric refraction, his observations were accurate to within 2 arc minutes (some to within about half an arc minute), at a time when most astronomers were happy with an accuracy within 15 arc minutes. In addition to the works already cited, he also published Astronomiae Instauratae Mechanica (Instruments for the Restored Astronomy), which included a description of his instruments, as well as an autobiographical account of his career and discoveries, in 1598. Astronomiae Instauratae Progymnasmata (Introductory Exercises Toward a Restored Astronomy), which discussed the motions of the Sun and Moon and gave the places of 777 fixed stars, was edited and published by Kepler in 1602.

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Nicolas Copernicus
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This page was last updated on 02/25/2017.