Tycho Brahe

Tycho Brahe framed by the family shields of his noble ancestors, in a 1586 portrait by Jacques de Gheyn. Credit: Museum of Fine Arts, Houston/Wikimedia Commons

Tycho Brahe (born Tyge Ottesen Brahe), Danish astronomer, astrologer, and alchemist, was born on December 14, 1546 in Knutstorp in Skaane, Denmark (now Sweden) into a Danish aristocratic family. When he was only two years old, Tycho was taken away to be raised by his wealthy uncle, and managed to avoid the usual custom of becoming a courtier, ending up in the service of the King. Instead, Tycho pursued his true interests in the humanities and the sciences, particularly astronomy. From 1559 he attended the University of Copenhagen and subsequently studied at universities in Leipzig, Wittenberg, Rostock, Basel, and Augsburg, before returning to Denmark in 1570. In 1566 he lost part of his nose in a duel over a mathematical formula and wore a prosthetic nose for the rest of his life.

   After publishing a book De nova stella (1573) on the nova of 1572, Tycho planned to leave Denmark. Having heard of Tycho’s plans, King Frederick II of Denmark offered Tycho in 1576 the isolated island of Hven in the strait off Copenhagen and funds for the establishment and maintenance of an observatory. For his observatory, Tycho designed massive instruments with which he hoped to obtain the most accurate observations ever. The observatory, called Uraniborg, and a nearby subterranean observatory called Stjerneborg, were equipped with exceptionally large and accurate instruments. At Uraniborg, Tycho made twenty years' worth of astronomical observations. He concentrated primarily on obtaining accurate positions of the stars and on observing the Sun, Moon, and planets in order to get the most precise understanding to date of their orbits and motions. Nearly all of his instruments were accurate to within a minute of arc, and some approached a limit of 30 seconds of arc.

 

Portrait of Tycho Brahe at age 50, c. 1596. Credit: Wikimedia Commons

 

   Following a disagreement with the new king, Christian IV, Tycho left Uraniborg to Germany. In 1599, he was appointed Imperial Mathematician to the Holy Roman Emperor, Rudolph II, in Prague. In 1600, Johannes Kepler (1571–1630) became his assistant, to help with mathematical calculations. Tycho died in Prague on October 24, 1601 from bladder complications that led to uremia.

 

   According to Kepler, Tycho's last words were:
 
   "Let me not seem to have lived in vain."

 

Tycho Brahe's largest instrument, the mural quadrant, from Tycho Brahe, Asrronomiae instauratae mechanica (Wandesbeck, 1598). Credit: Wikimedia Commons

   Tycho was the last major astronomer before the invention of the telescope, and is best known for the astronomical observations which led Kepler to his theories of the Solar system.

   On November 11, 1572, Tycho noticed a new, bright star in the constellation of Cassiopeia. The new star (nova stella), now known as a supernova SN 1572 or Tycho's Supernova, was bright enough to be visible during the daytime. Tycho was not the first to see the new star, but his observations determined that the star exhibited no diurnal parallax whatsoever, and therefore lay beyond the sphere of the Moon. It challenged the Aristotelian dogma of the immutability of the realm of stars. Tycho published his findings in a book entitled De nova stella (1573).

   In 1577, Tycho observed a spectacular comet (the Great Comet of 1577) and, by measuring its parallax, concluded that the comet was moving through space beyond the Moon, somewhere near the sphere of Venus. This challenged the Aristotelian perception that comets were atmospheric phenomena. The fact that the comet seemed to move across several planetary orbits subsequently led Tycho to denying the reality of celestial spheres. He published his account in De mundi aetherei recentioribus phaenomenis (1588).

   Tycho greatly admired Copernicus and the way the Copernican system explained the many links between planetary models and the position of the Sun. But he could not accept Copernican cosmology because of the lack of stellar parallax, incompatibility with Holy Scripture, and the physical repugnance of a moving Earth. In 1588, Tycho proposed a geoheliocentric cosmological system, with the five planets orbiting the Sun, and the Sun, Moon, and stars circling a stationary, central Earth. The Tychonic system remained a serious alternative to the Copernican system well into the 17th century.

   Tycho's observations of planetary positions were much more accurate than any made by his predecessors. They allowed Kepler, who (unlike Tycho) was a convinced follower of Copernicus, to deduce his three laws of planetary motion (1609, 1619) and to construct astronomical tables, which he published in 1627 as the Tabulae Rudolphinae (Rudolphine Tables), the accuracy of which largely convinced astronomers of the correctness of the Copernican theory.

 

The Tychonic geo-heliocentric system from Tycho Brahe, De mundi aetherei recentioribus phaenomenis liber secundus (1603). Credit: Library of Congress, Washington, DC

 

Portrait of Tycho Brahe in the book Astronomiae instauratae mechanica (1598) with a clearly visible nasal prosthesis

 

References:

J J O'Connor and E F Robertson, "Tycho Brahe", MacTutor History of Mathematics. School of Mathematics and Statistics, University of St Andrews, Scotland
William B. Ashworh Jr. in, History of Astronomy: An Encyclopedia, edited by John Lankdorf, Garland Encyclopedias in the History of Science (Vol. 1), 1997
J. Voelkel in, Encyclopedia of Astronomy and Astrophysics. Nature Publishing Group, 2001

 

© 2025, Andrew Mirecki