Tycho Brahe

gigatos | June 23, 2022


Tycho Brahe (listen), born Tyge Ottesen Brahe (December 14, 1546 – October 24, 1601), was a Danish astronomer, from a large family long associated with the affairs of the kingdom. His native region, Skåne, is now part of Sweden.

Tycho Brahe marked a break in the history of astronomy and more generally in the history of science. At a time when respect for tradition and the ancients still prevailed, he gave priority to observation, with the constant concern to validate his hypotheses with respect to these. He took great care in the manufacture and development of his instruments, which allowed him to collect a considerable amount of data. Although made with the naked eye, these measurements are, at their best, at least ten times more accurate than those of his predecessors in Europe. Thus, his observations of the supernova of 1572 led him to question the immutability of the supra-lunar world stated by Aristotle, a questioning confirmed by his observations of the great comet of 1577, which he highlighted as not being an atmospheric phenomenon (sub-lunar).

His very precise observations of the positions of the planet Mars played a decisive role in Johannes Kepler”s discovery of the trajectory of the planets and, more generally, of the three laws that govern their motion.

Although he was a great admirer of Nicolaus Copernicus, he did not decide to abandon geocentrism and preferred to develop a mixed system, called geo-heliocentric: the Earth remained immobile at the center of the universe, while the other planets revolved around the sun, also driven by the sun”s movement around the Earth. Although conceptually ruined by the discoveries of Kepler and then Newton, the system was supported throughout the 17th century by the Jesuits, who saw it as the only way to save the immobility of the Earth, which in their eyes was consistent with the Scriptures. This system was definitively invalidated by the discovery of the aberration of light, which empirically demonstrated the Earth”s annual motion.

As a young man, Tycho benefited from an education open to the sciences in a Protestant university system, still very much influenced by the ideas of Philipp Melanchthon. He first studied in Copenhagen, where he discovered astronomy in particular, and then spent many years at German Protestant universities.

Thanks to the support of King Frederick II of Denmark, Tycho Brahe enjoyed the use of the island of Ven for about twenty years and received a comfortable income to carry out his work. He had the palace of Uraniborg built there, which was his home, but above all a place of study and a true research center before its time, equipped with an observatory, but also a craft center for the manufacture of instruments and a printing press to distribute his work. He trained many students and received visitors from all over Europe.

After the death of his protector and the interregnum that followed, Tycho lost the support of his successor, Christian IV, and chose to emigrate. Welcomed by Emperor Rudolf II, who made him his imperial mathematician, he settled near Prague. There, Kepler joined him to become his assistant for almost a year and to inherit, at the death of the Danish astronomer in 1601, the latter”s exceptional observations.

In French, the name of the astronomer was often spelled Tycho-Brahé or Tycho Brahé.

The importance of Tycho Brahe in the history of astronomy has long been variously appreciated. When he died in 1601, he was the most famous scientist in Europe. At the end of the 18th century, Jean Sylvain Bailly saw, since antiquity, only Hipparchus who could be compared to him, without ignoring the importance of Copernicus whom Bailly considered “greater as a philosopher than as an astronomer”. However, Tycho was sometimes considered as a simple observer, certainly without rival, but not exploiting his observations himself, his theoretical contributions were often reduced to his geo-heliocentric system, seen as too complacent towards the religious prejudices of the time. Although the nineteenth century did not forget him, it was only in the second half of the twentieth century that this picture was largely completed and corrected and that Tycho found his place, at the forefront, in the history of astronomy and in the history of science. Thus he opens the second volume of René Taton and Curtis Wilson”s general history of astronomy, as the one who, by the primacy he gives to observations, inaugurates modern astronomy, at least on a par with Copernicus, whose heliocentrism was revolutionary, but whose practice had remained that of ancient astronomy.

As far as his life is concerned, historians benefit, in addition to their usual sources, from Pierre Gassendi”s biography, one of the first of its kind, written less than fifty years after the astronomer”s death. Tycho himself wrote a short autobiography, but Gassendi was able to supplement it with other sources, including interviews with members of his family. In 1890, the astronomer and historian of astronomy John Louis Emil Dreyer published a biography that has long been an authority, even if it does not take into account some of his own work, published later. Dreyer was also the principal editor of the complete works of Tycho Brahe published between 1913 and 1929. More recently, Victor Thoren”s biography, published in 1990, is a sum of Tycho”s life and work that takes into account the latest works published at the time of its publication, including those in Scandinavian languages.

Of high birth

Tycho Brahe was born in 1546 at his family”s castle in Knudstrup, Skåne, then a Danish province. He was the second of twelve children (eight of whom lived beyond infancy) of Otte Brahe (en) and Beate Bille (en) and their first son. His twin brother, to whom he will later write an ode, does not survive. His sister Sophia, who was to be his collaborator, was born ten years later. Both the Brahe family and the Bille family were of high and ancient nobility and closely associated with the affairs of the kingdom. His two grandfathers and four great-grandfathers were all members of the Rigsraad (or Riksråd), the council of the kingdom, which, with its twenty or so members, assisted the king, and even substituted for him on occasion. His father and uncles were or would be members of the council, as were two of his younger brothers, Steen and Axel. The Brahe family were landowners and swordsmen. Early converts to Protestantism, they took part in the seizure of power of king Christian III, who imposed Lutheranism in Denmark in 1536. The Bille family was more of a financier and a churchman. Almost all the bishops of Denmark were related to their family, but they also provided men of war for the defense of Catholicism. Their influence remained great, despite the advent of the Reformation, and the marriage alliance with the Brahe family was also, for Beate”s father, a way to maintain it.

At a very young age, Tycho was taken from his parents by his uncle Jorgen Brahe (en). The event, which historians consider likely to have taken place in his second year, is mentioned in his autobiography without further details or explanation. It remains difficult to interpret. Otte”s broken promise to his brother Jorgen? It turns out that Jorgen, whose wife was no more than twenty years old at the time of the kidnapping, will never have a child. Otte and Beate, who had a son, Steen, a year after Tycho”s birth, do not seem to have held the abduction against Jorgen, who, with his wife Inger Oxe, raised Tycho as if he were their own son, providing for his upbringing and education until Jorgen”s accidental death in 1565. The Oxe family is less ancient than those of the Brahe and Bille families, but has already provided several advisors to the Rigsraad. Inger was also the sister of Peder Oxe (en), whose financial and diplomatic skills would make him, apart from an eight-year period of exile, the most influential Danish statesman of the time.

It is under the influence of Inger Oxe, that the education of the young Tycho Brahe will be very different from that of his brothers.

Childhood and studies in Denmark

Few details are available about the childhood of the young Tycho Brahe. His uncle was established in the family manor of Tostrup (en), in the east of Skåne, but he also successively administered various strongholds, and it is probable that his nephew followed him on his travels. In 1552, he was appointed governor of Vordingborg Castle and the lands under it by King Christian III, and in 1555 Queen Mother Sophie (widow of Frederick I and mother-in-law of King Christian III) put him in charge of the nearby Nykøbing Castle, which put Jorgen in charge of a considerable number of fiefs. The king and his mother-in-law did not get along and in 1558 Jorgen lost the governance of Vordingborg, an event also linked to the disgrace of his brother-in-law Peder Oxe, who had his property confiscated, and went into exile the same year for eight years.

It is therefore likely that Tycho lived at the court of the lords, with frequent travel, until he was seven years old, at which time he is known to have begun his elementary education. For at least two centuries, this traditionally took place for young nobles in the school attached to the cathedral of an episcopal city, with the bishop or an important cleric providing accommodation. The Reformation did not change this tradition much, except that the Lutheran theologians, who came from the middle classes, took the place of the bishops, who were nobles, and imported another way of life, inspired by the one they had known during their studies in German universities, especially in Wittenberg. Tycho probably joined the cathedral school of Vordingborg, like his two younger brothers Steen and Axel (we know that they were enrolled at the one in Aalborg, the center of the fief governed by their father Otto). He was taught Latin language and grammar, religion, singing and probably elementary mathematics.

On April 19, 1559, Tycho joined the University of Copenhagen to complete his classical education, among others in the three arts of the medieval trivium, grammar, logic and rhetoric, considered at the time as useful for a political career. He also followed the teachings of the quadrivium, the four classical mathematical sciences, arithmetic, geometry, music and astronomy. These were revived by the Protestant theologian Philipp Melanchthon, a disciple and friend of Martin Luther and his principal second in command. His ideas had a great influence on the teaching of Lutheran universities and thus in Copenhagen. A partial eclipse of the sun took place in Copenhagen on August 21, 1560, which was too unspectacular to have been noticed by the young Tycho without being indicated to him, and which did not necessarily trigger his interest in astronomy, although Gassendi agreed. It was in Copenhagen that Tycho learned that astronomical events had regularities that allowed them to be predicted, that he began to explore astronomical and astrological literature, and more generally to open himself up to an intellectual universe that was very different from that of the Brahe family. In this context, Tycho”s particular interest in astronomy is not necessarily exceptional. Tycho acquired the books that the professor of mathematics at the university used for his teaching, first the treatise on the sphere (de sphaera mundi) by Johannes de Sacrobosco, then the following year the Cosmography (Cosmographia) by Peter Apian and the trigonometry (De triangulis omnimodus) by Regiomontanus. These works bear the inscription “Tycho Brahe, Anno 1561”, the first known occurrence of the Latin form of his first name. Tycho also obtained the ephemerides of Joannes Stadius based on the Prutenic Tables (which themselves were based on the work of Copernicus).

Education at German universities

At the age of fifteen, Tycho had to complete his education abroad. For his brothers, this meant serving as a squire in German courts, but Tycho followed the path of Peder Oxe and attended German universities during three successive journeys, which lasted more than nine years, from 1561 to 1570.

For his family it is a question of giving him the training which will enable him to hold his rank in the service of the kingdom. But at the end of the first trip, his vocation for sciences is affirmed and in particular for astronomy.

His travels also allowed him to meet many humanists who were scientists or interested in science. He sympathized with some of them with whom he remained in correspondence.

Tycho left in 1561 accompanied by a tutor four years older, the future historian Anders Sørensen Vedel (en), who was responsible for his education and whose friendship he would maintain throughout his life. Their destination was the University of Leipzig, where they stayed for three years. Tycho followed the classical studies planned by his family, but secretly acquired and studied books, ephemerides and astronomical instruments.

He began to observe the movement of the planets, armed with a celestial globe “no bigger than your fist” on which he plotted the alignments between the planet in question and two stars that he had spotted with a simple string. This rudimentary equipment was enough for the young apprentice astronomer of sixteen years to highlight important differences with the positions predicted by the ephemerides, whether they were based on the Alphonsian Tables which used the system of Ptolemy, or on the Prutonic Tables which used the system of Copernicus (even if the latter appeared slightly superior).

In 1563, he acquired a new instrument, a large compass that allowed him to measure by sight the angular distance between two stars, and in August of the same year he inaugurated his first diary of observations by the approach of the planets Jupiter and Saturn, a phenomenon that occurs every twenty years. There again he could only note an error of nearly one month for the Alphonsine Tables and which is still of several days for the Prutenic Tables. According to what Tycho will declare later, it is from this time that he decides to improve this state of affairs, in particular by accumulating observations.

Tycho also acquired a book of astrology by Johannes Garcaeus (de) and in the same year began to practice writing horoscopes.

In 1564 he was eighteen years old, and Vedel could hardly compel him to devote himself to his planned studies. He met Bartholomäus Scultetus (de), with whom he deepened his knowledge of astronomy, but also learned cartography and geography… He acquired his first professional astronomical instrument, a radius astronomicus (or Jacob”s staff) of one meter long designed according to the plans of Gemma Frisius by the latter”s nephew, Gualter Arscenius. The wooden and brass instrument is sufficiently cumbersome and expensive to have not passed unnoticed by Vedel: Tycho asserts himself and does not dissimulate any more his intention to devote himself to astronomy.

In the spring of 1565, Tycho and his tutor decided to return to Denmark. The war with Sweden, which had broken out in 1563 and was to last seven years, did not seem to bother them, but it was not without consequences for Tycho. His uncle and adoptive father Jorgen, after having captured in an uncertain naval battle the admiral of the Swedish fleet and his ship, was appointed vice-admiral of the Danish fleet. But in 1565, during a return to port, he died from a dive in the waters of Copenhagen, in the company of his king (who escaped). He would have tried to rescue Frederick II who had fallen into the water while they were both returning from a tavern. Jorgen did not have the time, as he had planned, to make Tycho his sole heir. Jorgen”s fortune and lands will be managed in usufruct by his wife Inger Oxe who will live until 1591, but Tycho passes, until his majority, under the responsibility of his natural parents. Tycho also lost his maternal grandfather who died while commanding the defense of the fortress of Bahus. Tycho stays in Denmark for almost a year, the time it takes to convince his soldier father to let him continue his studies, when war offers so many opportunities to someone of his social class.

In 1566, Tycho returned to the continent to spend a few months at the University of Wittenberg, the cradle of Lutheranism, where he found Vedel and probably Sculetus. Driven out of the city by an epidemic, he retreated to the University of Rostock which, like Wittenberg, was attended by many Danes. There he observed a lunar eclipse on October 28 and made public his astrological interpretation: the event announced the death of the Sultan of Turkey Soliman the Magnificent. Unfortunately for Tycho, it turns out that, if Suleiman did die, it was a few weeks before the eclipse. There must have been some mockery and, according to Thoren, this could have been the cause of an argument with a distant cousin, Manderup Parsberg – but historians are left to speculate on the origin of this one. Nevertheless, the affair ended in a duel. These were common at the time between young nobles and could end tragically. The affair was not so serious for Tycho, but it was very close: his cousin cut off the bridge of his nose, and, if Tycho survived the wound, he was disfigured for life. He later wore a false nose, which can be seen on some of his portraits and which would have been made of gold and silver, but this was not reported until after his death (and reported by Gassendi).

During the exhumation of Tycho”s body in 1901, traces of copper were found at the site of his nose, which is not necessarily incompatible with the legend, as Tycho may have had several prostheses.

It is possible that his injury was the cause of his later interest in medicine and alchemy. In Rostock, he was able to follow the teachings of two representatives of the new empiricist approach to medicine, Heinrich Brucaeus (de) and Levinus Battus (de), especially since both were also interested in astronomy. While Brucaeus, who studied anatomy, was very hostile to astrology, this was not the case for Battus, a follower of Paracelsus and his global vision of man in the universe, which was also of great interest to Tycho.

During 1567, Tycho returns to Denmark. Peder Oxe had returned in grace the previous year. Appointed Rigshofmester (en), the equivalent of prime minister, he dramatically improved the kingdom”s finances and made peace (in 1570) with Sweden. But once again, Tycho did not take advantage of the opportunities that the support of his uncle by adoption brought him and, despite what his family thought, preferred to return to Rostock at the end of 1567 to continue his studies, where he stayed for a while with Levinus Battus and devoted himself (most probably) to medicine and alchemy. However, he only stayed there for five months and then led an itinerant life for some time. He lingers a little in Basel where he meets the young Hugo Blotius (de) with whom he tries to build quadrants, goes to Freiburg where he admires the astronomical models of Erasmus Oswald Schreckenfuchs (en), is received by Cyprianus Leovitius (en) (whose ephemerides he appreciated) in Lauingen, meets Philipp Apian (en) (Peter”s son) in Ingolstadt… But it was in Augsburg that he finally settled in the spring of 1569 and developed his first astronomical instruments.

Like all cities of this importance, Augsburg had its own circle of humanists who welcomed Tycho. He sympathized with some of them, such as the scholar Hieronymus Wolf, the mayor Paul Hainzel (de) who financed the construction of his gigantic quadrant, and the teacher at the Augsburg high school Johannes Major. But the young Dane also found an extremely capable craftsman in Augsburg, Christoph Schissler, who enabled him to make the instruments he designed.

With the help and financial support of Paul Hainzel, Tycho had a quadrant with a radius of 5.5 meters built in Augsburg in early 1570, the size he considered necessary to achieve the accuracy of one minute of arc. He used it for some observations reported in his diary. The instrument will remain the largest of his production and attracts on its creator the attention of the most famous philosopher of the time, Pierre de La Ramée, who arrived in Augsburg in April 1570 and who will quote in his works the instrument of the young Dane “Bracheus”.

La Ramée was a convinced empiricist, very hostile to the Aristotelianism of his contemporaries, and who promoted in his writings a science without any hypothesis, based only on observation. As he proposed to Rheticus, it would be “sufficient” to establish ephemerides over the duration of the Great Year, the one at the end of which the universe is supposed to find the same configuration, and one could then forget the heliocentric and geocentric hypotheses, the mathematical models, their epicycles, eccentrics and other equants.

Tycho discussed with La Ramée the radical reform of astronomy that the latter proposed. If they agreed on the primacy of observation, Tycho did not accept the abandonment of hypotheses and compared astronomy to geometry where axioms were necessary, even if he accepted that these hypotheses could evolve (at the time of Tycho, the dogma of the astronomers magnified by Copernicus was that of uniform circular motion: the motion of the celestial bodies must be decomposed from this). He also considered the concept of a harmonious and orderly cosmos, as put forward by Melanchthon, to be necessary. Tycho did not adopt the conceptions of La Ramée and reproached the philosopher for not knowing the practice of astronomy.

At the end of May 1570, Tycho, perhaps alerted by bad news about his father”s health, left Augsburg to return to Denmark. He probably arrived at the beginning of December 1570 at Otte Brahe”s castle in Helsingborg. The latter died on May 9, 1571. Although he had left his affairs in good order, the heirs were numerous and the complex succession was not settled until 1574. It made Tycho financially independent, even though he did not have the income he could have hoped for if he had been the heir of his uncle Jorge, as Jorge had envisaged before his death.

Installation in Denmark

Shortly after his father”s death, Tycho moved in with his maternal uncle Steen Bille, with whom he had become friendly and who welcomed him to his estate, the old abbey of Herrevad, a few kilometers from the family castle. Steen Bille was a humanist scholar, very interested in alchemy, and Tycho set up his own laboratory on the estate.

It was also around this time that he met Kirsten Jørgensdatter, who became his wife and the mother of his children, and with whom he was able to settle in Herrevad. Historians have been reduced to hypotheses about her origins, perhaps the daughter of a pastor in the vicinity of Knudstrup. One thing is certain: she was not a noblewoman, which forbids an official marriage to Tycho. At the time, however, Tycho could invoke the old Danish law that granted a wife status to a woman who lived in a marriage long enough with a man. This was not exceptional, but Tycho thus deprived himself of the alliance between great families that a marriage represented in his milieu and ostensibly marginalized himself among people of his rank.

According to his own words, Tycho devoted most of his time to alchemy. However, it was in Herrevad that, on November 11, 1572, Tycho made his first important observation, the one that really launched his career as an astronomer: a “new star” (nova stella) – its brightness exceeded that of Sirius, Vega and even Venus – appeared in the constellation of Cassiopeia. Astronomers of the twentieth century were able to identify it from the observations of Tycho and conclude that it was what is now called a type I supernova, which they named SN 1572. It remained observable until March 1574.

Thanks to the instruments at his disposal, Tycho quickly established that the “new star” is immobile with respect to the stars that surround it. It cannot be a planet or a comet, and the absence of observable diurnal parallax shows that the object is necessarily beyond the moon, which destroys the then commonly accepted Aristotelian conception of a division of the heavens into a sub-lunar world subject to change and a supra-lunar world unchanging.

These revolutionary conclusions are highlighted in a short treatise, De Nova Stella, which he had published the following year at the instigation of Peder Oxe. The activity at Herrevad was of interest to the king and his Grand Intendant. One chapter of the treatise is devoted to astrological aspects and their political consequences, and it probably did not have a great public echo, given its limited circulation, but Tycho sent it to his friends, scholars and scientists throughout Europe.

In September 1574, he gave a lecture at the University of Copenhagen, which was followed by several courses in which he explained Copernicus” theory. Peder Jakobsen Flemløse, who was to become one of his most faithful assistants, was among his students.

In 1575, however, he left his teaching for a new trip to Germany and Italy. It is no longer a simple study trip. Tycho had the support of Frederick II and it seems that the latter had commissioned him to attract artists, craftsmen and engineers to Denmark. On the other hand, Tycho, now financially autonomous with the settlement of his father”s estate, planned to emigrate to Basel, a city at the crossroads of Germany, France and Italy.

At his return at the end of 1575, his sovereign receives him and seems fully satisfied, but the reward which he proposes to Tycho, a royal fief as it is usual for someone of the rank of the young Dane, does not interest the latter.

At the beginning of 1576, the king, informed of Tycho”s emigration project, offered him the island of Ven and considerable means to carry out his scientific work. The offer was exceptional and Tycho could not refuse it. He was able to establish on the island a true research center which became famous in all Europe: Uraniborg.

Tycho had Uraniborg (“Urania”s Palace” or “Palace of the Heavens”, Urania being the muse of Astronomy) built, the first stone of which was laid in September 1576 and which became the most important observatory in Europe. He had supreme authority over the domain and received income from the work of the islanders. He also had a palace built, financed by the king and lasting four years, from 1576 to 1580. It was a luxurious building that included a workshop for the construction of astronomical instruments, a printing house for the publication of his works, and an alchemy laboratory.

Uraniborg quickly became an important and renowned scientific center, which attracted students and astronomers from all over Europe. Tycho Brahe was very meticulous and kept all the data of his observations, which allowed him to establish the most complete and precise catalog of stars of the time. He is considered by his colleagues and contemporaries as the most accurate observer. All his observations were made before the invention of the telescope and the telescope. It was also here that Tycho Brahe developed his system of the world, which was a sort of conciliation between the system of Ptolemy and that of Copernicus.

In 1577, he began his observations and on November 13 of the same year, he made the discovery of the comet which is the basis of his second work on the movements De Mundi atherei recentioribus Phoenomenus Progymnasmatum published in 1587.he built in 1584 an astronomical observatory buried that he called Stjerneborg (palace of the stars). This one comprises underground rooms in which are installed instruments and whose roofs, or domes, exceed the ground.

Tycho Brahe was also a pharmacist. His laboratory in the basement of Uraniborg had sixteen furnaces, some connected to distillers. He spent most of his time researching remedies, some of which were based on mercuric sulfate to treat skin diseases such as those caused by syphilis. He also had works by his students printed in Uraniborg, which he supervised.

King Frederick II died in 1588, his son Christian IV was only ten years old. Tycho Brahe, although he lost his patron, retained the support of the Danish government, ensured by a Council of Regency in the hands of the great Danish aristocracy. Tycho was concerned about the durability of his “research center”, but also about the future of his children who were not noble, as their mother was not. He obtains from the Council of Regency an official declaration ensuring that his scientific establishment of Hven would be maintained with the resources necessary to its activity and a direction being able to be ensured by commoners, with an order of succession which privileges the family of Tycho. The declaration is confirmed in 1589.

During the regency, the scientific activity in Hven continues. Christian Sørensen Longomontanus, who will become a close friend of Tycho and his principal assistant, is recruited in 1589. The mathematician and astronomer Christoph Rothmann (of) of Cassel, correspondent of long date of Tycho spends August 1590 at Hven.

Tycho also received the great ones of this world like king Jacques VI of Scotland who came to marry in 1590 an elder sister of Christian IV. The young king of Denmark himself and his court visited him in 1592.

Christian IV was crowned in August 1596: the Regency came to an end, and Danish power became much less favorable to Tycho. Christoffer Walkendorf (en), who had been ousted from the Regency Council by a faction close to Tycho, became Rigshofmester (en), the most important position in the government, which had been vacant since the death of Peder Oxe (en). Christian IV and his two main ministers, Christoffer Walkendorf and Chancellor Christian Friis (da), favored strong power in the hands of a monarch of divine right and opposed the oligarchic regime reinforced by the Council of Regency. As early as 1596 Tycho saw himself withdrawing a fief in Norway which had been allotted to him by Frederick II, his brothers and relatives often suffered similar losses. Tycho invokes in vain the engagements of Frederic II and the declaration of the Council of Regency about Hven. At the beginning of 1597, he loses an important annual pension which was paid to him since 1582. These two decisions make him lose a third of his annual income.

In April 1597, Tycho decides to leave Hven with his family and his close relations for Copenhagen. He embarks the majority of his instruments, leaving only those which cannot be dismounted, his printing presses, his library.

Tycho also made mistakes: as a canon of the chapel of Roskilde Cathedral, where King Frederick II and his two predecessors were buried, he allowed the vault to deteriorate, ignored in 1593 the injunctions to have it repaired by the young Christian IV, still a minor, and was slow to react. The office of canon was finally withdrawn from him in June 1597.

Subjected to vexations – he was forbidden to install his instruments on top of the city walls, above his home – he finally left Denmark for Germany in June 1597, still in the company of his relatives and his instruments, and never returned to Denmark.

Exile and end of life

He traveled for a few years and then, in 1599, moved to Benateck Castle near Prague where he worked as an imperial mathematician at the court of Emperor Rudolf II. He died in Prague in 1601. On his deathbed he was delirious, but in his moments of respite he said to Kepler: “Ne frustra vixisse videar!” (make sure that I don”t appear to have lived in vain!), because he realized that he had only made Progymnasmata (preliminary works). Kepler responded to this last wish by publishing Astronomiae instauratae progymnasmata in 1602.

He died of a stone or septicemia, which may have been caused by holding his urine for too long during a several-hour carriage ride with Emperor Rudolph II or a long meal at the imperial court in Prague. It is also possible that Tycho Brahe was poisoned, as rumors of this appeared after his death (see below). His instruments were kept there for a long time, but were eventually lost.

Like most astronomers before him, Tycho Brahe believed in astrology. He calculated his own birth chart: “Tycho Brahe, born on December 14, 1546 at 10:47 a.m. from Greenwich in Scania (Denmark). Sun in 2°07 Capricorn, AS in 16°38 Aquarius, Moon in 23°11 Virgo, MC in 15°19 Sagittarius.”

He is buried in the church of Our Lady of Týn, near the astronomical clock in Prague.

At his death, his important team of scholars and craftsmen spread throughout Europe and participated in experimental academies such as the Academy of Secrets, then the Academy of the Lynceans (1603) of Giambattista della Porta (1535-1615) and other followers of natural philosophy such as Girolamo Ruscelli, or the Accademia del Cimento.

The asteroid (1677) Tycho Brahe was named in his honor, as well as a lunar crater and a Martian crater.


SN 1572 (or Tycho”s Nova) is a supernova that occurred in the constellation of Cassiopeia, and one of the few to have been visible to the naked eye.

It was observed on November 11, 1572 by Tycho Brahe, from the Abbey of Herrevad, when it was brighter than Venus, with an apparent magnitude of -4. It stopped being visible from March 1574.

In fact, it seems that Brahe is not really the first to have observed it, it would have been seen by Wolfgang Schuler from November 6, 1572, by John Dee and his disciple Thomas Digges, then by the Italian astronomer Francesco Maurolico. But Brahe is the first to have described and studied it in detail.

First, Tycho Brahe pointed out that the object has no diurnal parallax in the context of fixed background stars. This implies that it was necessarily farther away than the Moon and the planets, which have such parallaxes. Then, he notes that, for several months, the object did not change its position relative to the fixed stars, as do the planets. This inspired him to conclude that the new celestial object was not a planet, but a fixed star in the stellar domain, beyond all the planets.

He published a small book on this subject called De Stella Nova, On the new star (1573). We know today that this supernova is located 7,500 light years from Earth.

The appearance of the supernova of 1572 is one of the two or three most important events in the history of astronomy. The “new star” helped to break the old representations of the sky, and triggered a revolution in astronomy. This discovery allowed for better catalogued astrometric classifications and made it necessary to use more accurate astronomical observational instruments. The Supernova of 1572 is often referred to as “Tycho”s Supernova” because of the extensive work that Tycho Brahe had done on it.

The great comet of 1577

In 1577, Tycho does not have yet his best instruments, but he acquires at the beginning of the year his first clock which gives the hour to the second, and, after an unsuccessful test, makes build an astronomical quadrant which gives him satisfaction.

One evening in November, he noticed for the first time a new star that turned out to be the comet he had been waiting to observe for a long time. The great comet of 1577 (C

The observation of this one is not simple. It is close to the Sun and, at its appearance, is visible only one hour after the sunset. Tycho will be able to observe it until January of the following year. He tried to calculate its diurnal parallax, by reconstructing the apparent movement of the comet, and by comparing it with that of the Moon. He ends up demonstrating that the diurnal parallax is insignificant, and gives an increase which relegates it necessarily beyond the Moon, at least four times further.

This is an essential result: it makes the comet a celestial body contrary to what Aristotle had theorized in The Meteorologicals. For Aristotle, comets are atmospheric phenomena that form below the Moon. As a neutral observer, Tycho examined all the data collected as well as his own. For him, the result was clear: the comet had to describe an orbit around the Sun “well beyond the Moon”, intersecting those of the planets. He concluded that the planets did not rest on transparent solid spheres (the famous “crystal spheres” of Aristotle) that Georg von Purbach had reinstated in his representation of the celestial sphere. Although he had retained geocentrism, he questioned two important points of ancient models to which some of his contemporaries were still attached: the “solidity” of the spheres and the immutability of supra-lunar space.


At the time of the conjunction of Jupiter and Saturn in 1563, Tycho Brahe realized that the precision of the astronomical tables available at his time was insufficient. Convinced that they needed to be improved, he invested in the improvement and creation of measuring instruments. It is with the crossbow that he made his first measurements with a limited precision. To refine these, he invented a kind of sextant, whose opening is on sixty degrees (hence its name). This invention allowed him in 1572 to measure the position of the supernova located in the constellation of Cassiopeia. Later, in 1581, he built a sextant of one meter fifty mounted on a spherical pivot.

Tycho improved or invented a dozen different instruments, some of which, before their further development and use in astronomy, were first used in maritime navigation. One of the best known was the wall quadrant with a radius of two meters, with which it was possible to measure declination to within ten seconds of arc.

He also had armillary spheres built, one of which had a diameter of nearly three meters. This one was used to measure the coordinates of the stars in the sky as precisely as possible and to have a better representation of the movement of the celestial bodies observed.

Tycho Brahe prefigured the end of the observational research of the sky without the help of the lens, which will allow him a little later to make a leap forward thanks to the astronomical telescope of Galileo and the telescope with concave mirror of Isaac Newton. His vigilance and perseverance allowed him to make precise measurements by means of instrument development and numerous conversions using spherical trigonometry. He is recognized as a leading scientist for the accuracy of his astronomical measurements for the time and his catalog of stars that Johannes Kepler later completed.

Geo-heliocentric model

Tycho gave himself a discipline of daily observation; he trained a whole generation of astronomers, inculcating in them the art of observation and deduced from those that he carried out a system, known as “of Tycho Brahe”, elaborated from the geocentric theory of Ptolemy (about 90 – about 168), from the mixed theory of Heraclides of Pontus (IVth century BC), for whom the Sun orbits around the Earth, while the five planets revolve around the Sun, and the heliocentric theory of Copernicus. C.), for whom the Sun orbits the Earth, while the five planets revolve around the Sun, and the heliocentric theory of Copernicus. In Tycho Brahe”s theory, the Sun and Moon revolve around the immobile Earth, while Mercury, Venus, Mars, Jupiter and Saturn revolve around the Sun.

The system of Copernicus (1473 – 1543) was declared contrary to the Bible by the Church in 1616. The system of Tycho Brahe was adopted by the Jesuits.

Kepler was unable to convince Tycho to adopt the heliocentric model of the solar system. Brahe seems not to have had any objection in principle, but he was opposed to it for reasons related to observations. Indeed, he considered that if the Earth orbited the Sun annually, there should be an observable stellar parallax over a period of six months, during which the orientation angle of a star would change, which was not perceptible. Taking up Brahe”s theses during Galileo”s trial, the holy inquisitor Robert Bellarmine objected that, if the Earth moved, a parallax should be observed. But since no parallax had been measured, this fact became an argument against heliocentrism. Galileo replied that the stars were too far away for parallax to be seen and measured with the instruments of the time. In the years that followed, Galileo, with his observation of the phases of Venus in 1610, invalidated the Ptolemaic system. Brahe”s system then became the main competitor to Copernicus”. The Catholic Church eventually abandoned Ptolemy”s geocentric system in favor of Tycho Brahe”s system, which was more consistent with observations.

It was during the year 1729 that James Bradley succeeded in proving the self-movement of the Earth relative to the fixed stars, according to his experimental demonstration of stellar aberration. Bradley obtained a maximum displacement of the aberration of the order of twenty seconds of arc, a very small value that could not be observed by instruments designed before the beginning of the 17th century. These new observations led to the elimination of Tycho Brahe”s system. As for parallaxes, they were only observed a century later by Friedrich Wilhelm Bessel in 1828.

In spite of his error, Tycho was part of a way of thinking based on observation and experimentation of the world, as was also the case for Kepler and Galileo. He was thus opposed to a way of thinking based on the choice of only theoretical systems, such as that of Aristotle, which nevertheless influenced astronomical research for centuries, or that of Copernicus, which, in many respects, remained firmly anchored in the tradition of the Ancients.

Tycho was the last of the astronomers of the era before the invention of the telescope. When he was seventeen years old, during a conjunction of Jupiter with Saturn, Tycho realized that all the astronomical tables did not agree and that it was almost impossible to make any prediction. This fact had a great influence on his life”s project. He devoted his life to finding a solution to this problem. Through his observations, he collected a mountain of data that led him to map the sky and produce reliable data that allowed Kepler to establish and publish the Rudolphine tables in 1627. He trained a whole generation of astronomers in his school in Uraniborg, using his methods of observation and his instruments. He recruited the best, including Peder Jakobsen Flemløse and Elias Olsen Morsing, Kristen Sørensen Langberg (Longomontanus) and Johannes Kepler to help him realize this colossal project.

During his career, he constantly refined his observation instruments. In May 1598, he published the stellar catalog with the positions of 1,004 stars. For the time, it is the best world reference of astral precision. It is thanks to this project that, a few years later, all these observations of the trajectories of the planets allowed Johannes Kepler, his assistant, to analyze the path of the stars and to bring out three gems: Kepler”s universal laws. Later, Isaac Newton demonstrated them mathematically and deduced the universal law of gravitation.

He was the first astronomer to perceive the refraction of light and to establish a complete table to correct astronomical measurements due to this effect.

He deduced from his observations a planetary system, called “Tycho Brahe”s system”. It is a hybrid system between the geocentric theory and the heliocentric theory. The Tycho system became the main competitor to Copernicus” system. A dispute arose with the astronomer Ursus, who had visited Uraniborg with Heinrich Rantzau, a friend of Tycho Brahe, about the authorship of his system. In the end, it appears that the latter was inspired by the model of Paul Wittich (1546-1586).

Tycho improved or invented a dozen different instruments, some of which, before their improvement and use in astronomy, were first used in maritime navigation. With his observations of the Great Comet of 1577, Tycho demonstrated that it had no measurable diurnal parallax, and that this object must be located well beyond the influence of the Earth. He thus showed that comets are not phenomena of the Earth”s atmosphere.

Tycho was an organizer, he knew how to use all that astronomical science of the time possessed. In particular, he acquired the books of Paul Wittich. His library was enriched by exchanges of books and purchases. Tycho sent his publications to princes and schools throughout the continent and received many books as gifts. To build up his extensive library he did not hesitate to buy complete libraries. Through his contacts and travels, he collected a wealth of information related to his project. To process this mass of data, Paul Wittich taught Tycho his new method of prostapheresis, an algorithm that was the precursor of logarithms, thus accelerating the production of his team”s calculations.

Tycho Brahe asked Johannes Kepler to calculate the precise orbit of Mars, for which he had noticed an eccentricity in the trajectory, considered as an anomaly at a time when, according to the system of epicycles of Hipparchus, taken up by Ptolemy, it was still sometimes thought that the motions of the planets described circles, perfect figures. Tycho therefore thought of constructing eccentrics for the planetary orbits. Such eccentric circles had been accepted since antiquity, through the epicycles, for the Moon and the Sun.

Thanks to Tycho Brahe”s meticulous observations, Johannes Kepler was able to develop the scientific basis of celestial mechanics based on the heliocentric system that Isaac Newton brought to its conclusion. Already with Tycho Brahe, the ancient models were no longer adapted and a total reworking of the geometry of the orbits and the tables was necessary. However, Brahe, imbued with religious scruples and rejecting Copernicus” theoretical system, sought to create a model of representation of the world that was a compromise between Copernicus and Ptolemy. His system, which proved to be complicated, was not followed by his peers. However, at the same time that Galileo was forced to recant, Gassendi accepted his system, albeit without much conviction, and the Jesuit Riccioli proposed a variant. It should be noted, therefore, that from Brahe”s model, it becomes possible to consider the heliocentrism of the planets (to the exclusion of the Earth) without being condemned by the Church. The ecclesiastical faith in the ancient model was shaken, preluding its de facto abandonment by Pope Benedict XIV around 1750.

In 1901, on the occasion of the tercentenary of his death, his tomb was opened and an autopsy was performed to verify that it was indeed his body. Hairs from his beard and hair were taken and after the fall of the Berlin Wall, the new Czech Republic authorized the Danes to plant their flag next to the astronomer”s tomb in 1991, offering the Danish ambassador hairs from Brahe”s beard during this official ceremony. These hairs were analyzed in 1992 and found to contain abnormally high levels of mercury, which could be explained by the use of this metal in Brahe”s alchemy experiments.

To elucidate the reason of his death, a study was made in 1996 by J. Pallon of the Institute of Physics of the University of Lund, Sweden. She studied more precisely the roots of his hair where concentrations of gold from 20 to 100 times higher than normal appeared until 2 months before his death. Her report concludes: “By observing the growth rate of the hair, it was concluded that Brahe was poisoned by mercury one day before his death. It is unlikely that he was murdered, in spite of a thesis suspecting Kepler”s involvement. It is more likely, in the case of the mercury poisoning thesis, that he triggered his own death by taking a mercury-rich remedy he had made the day before his death to cure himself. He wanted to cure his urinary system disorders (prostatic hypertrophy or, less likely, kidney stones). According to the analyses, there was no explosion of the bladder, but the mercury in his own preparations led to the uremia from which he died.”

Peter Andersen, a medievalist professor in Strasbourg, evokes the hypothesis of a plot fomented by King Christian. The professor found in the Swedish National Archives in Stockholm the diary of Erik Brahe, a distant cousin of the astronomer, written in a cryptic alphabet and which relates his contacts with Prince Johan, the younger brother of Christian IV. Erik Brahe would have poisoned Tycho on the indirect order of the king. The motive of the crime would be revenge: either the king was manipulated by his personal adviser Jon Jakobsen, a convinced Copernican and fierce enemy of Tycho Brahe. Or the king wanted to eliminate Brahe, who had been the lover of his mother, Queen Sophie of Mecklenburg-Güstrow, and possibly his father.

In 2010, Tycho”s body was exhumed again in order to carry out the analyses that advances in technology allow. The University of Aarhus publishes in 2012 the results of the examination of bones and teeth, which reveal a normal level of mercury in the last days of his life. Finally, after 400 years of mystery, Danish and Czech scientists conclude that Tycho Brahe died a natural death.

The asteroid (1677) Tycho Brahe is named after him.

Databases and dictionaries


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