Tycho Brahe

Tycho Brahe is considered the greatest observer of the period before the invention of the telescope and an innovator in astronomical studies.

Impressed by the solar eclipse of 1560, Tycho Brahe devoted himself to astronomy studies from a very young age.

Tycho Brahe discovered a strange Star

In 1572, a very bright star appeared in the constellation Cassiopeia.

Cassiopeia constellation. Credit: Wikipedia. Author:  IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg).

It came to have the luminosity of Jupiter and then slowly faded, although it remained visible until March 1574.

Tycho observed it for a year and a half, trying to calculate the distance with his instruments (he used the parallax method).

He realized that the star lacked parallax, which was equivalent to admitting that it was at an infinite distance, that is, that it belonged to the sphere of the fixed stars.

Supernova 1572
Remnant of SN 1572 as seen in X-ray light from the Chandra X-ray Observatory. Credit: Wikipedia

Tycho Brahe published the results of his work and caused a real revolution in the field of knowledge of the laws of celestial mechanics.

The newly formed star remained in the sky for a year and a half.

It began as a small, barely visible light, grew rapidly in intensity, became a luminary that eclipsed the rest of the stars in its constellation.

The star reached its climax presenting itself as the most visible star in the sky, brighter than Venus and clearly observable. in broad daylight.

It was the explosion of a supernova. At the site where the 1572 supernova was located, we can now see a gigantic gas nebula, expanding at several thousand kilometers per second, even more than four centuries after the explosion that destroyed its star.

The King of Denmark rewarded Tycho Brahe

Tycho captured the admiration of the King of Denmark Frederick I who, in 1576, gave him the small island of Hven, in the Strait of Sund, today Swedish territory.

Frederick I
Portrait of Frederick I King of Denmark and Norway. Credit: web en.wikipedia.org/wiki
Hven Island
Hven Island is best known as the location of Tycho Brahe’s 16th century observatories. Credit: web en.wikipedia.org/wiki

Here, Tycho had the largest observatory of his time built, which he called Uraniborg, that is, “city of heaven.”

He endowed the observatory with monumental and perfected instruments, some of which were devised by himself:

  • mural quadrants,
  • sextants,
  • armillary spheres,
  • squares and gnomons with gigantic graduated scales to obtain the best precision then possible in determining the celestial coordinates and the other astronomical measurements.

    Tycho Instruments
    Caption Illustration of an equatorial armillary sphere, containing one and a half circles, in Tycho Brahe’s observatory. Credit NYPL / Science Source/ Science Photo Library

From Le Grand Atlas de Cosmografia Blaviane, by the Dutch cartographer Johan Blaeu. Riccardana Library; Florence, Italy.

Tycho Brahe followed the path of a comet

With his instruments, he had followed the course of a comet that appeared on November 13, 1577.

By measuring its parallax, to calculate the distance, he concluded that it was approximately 230 Earth radii, that is, beyond the Moon, which is 60 Earth radii.

Comet 1577
The Great Comet of 1577, seen over Prague on November 12.  Credit: Wikipedia. Engraving made by Jiri Daschitzky. Web: “en.wikipedia.org/wiki/Great_Comet_of_1577”.

In 1588, he denied, not with simple dissertations, but with evidence based on observations and measurements, another theory that was universally accepted at that time: that comets were in the Earth’s atmosphere.

Tycho rejected the Copernican system for consistency with his observations.

He reasoned this way: If the Earth were to rotate in an orbit around the Sun, as Copernicus thought, the observer should notice an annual shift (parallax) in the positions of the fixed stars.

Since he never managed to measure this displacement, he deduced that Copernicus was in error.

Tycho’s problem was the insufficient precision of his instruments that did not allow him to appreciate the small parallax of the stars.

After the death of the King of Denmark, which occurred in 1588, Tycho Brahe left the island of Hven and settled in Benatky Castle, near Prague, becoming the official mathematician of Emperor Rudolph II.

Tycho Brahe moved his residence to Prague

Here in Benatky he was joined in 1600 by the young Johannes Kepler, with whom he had a fruitful collaboration in the last years of his life.

Castle Benatky
The castle in Benátky where Tycho Brahe lived from August 1599 to June 1600. Credit: Autor H. Raab web: “es.wikipedia.org/wiki/”

When he died, in 1601, Brahe left Kepler the annotations made throughout years and years of study, in the hope that he would be able to demonstrate his theory about the structure of the Universe.

And so it was, because thanks to the observations made by Tycho, Kepler was able to realize that the planets do not describe circular orbits, but elliptical ones.

Planets orbits
Venus and Mercury look close to the Sun because they are actually closer to the Sun. Credit: Biosphere Project.