Tycho Brahe

This article is about the astronomer Tycho Brahe. For other uses, see Tycho Brahe (disambiguation).

Tycho Ottesen Brahe
Born	14 December 1546 Knutstorp Castle, Scania
Died	24 October 1601 (aged 54) Prague
Nationality	Danish
Education	Private
Occupation(s)	Nobleman, Astronomer
Spouse	Kirstine Barbara Jørgensdatter
Children	8
Parent(s)	Otte Brahe and Beate Bille
Signature

Monument of Tycho Brahe and Johannes Kepler in Prague

Tycho Brahe (14 December 1546 – 24 October 1601), born Tyge Ottesen Brahe, was a Danish nobleman known for his accurate and comprehensive astronomical and planetary observations. Coming from Scania, then part of Denmark, now part of modern-day Sweden, Tycho was well known in his lifetime as an astronomer and alchemist.

In his De nova stella (Of new stars) of 1573, he refuted the theory of the celestial spheres by showing the celestial heavens were not in an immutable or unchanging state of perfection as previously assumed by Aristotle and Ptolemy. His precise measurements indicated that "new stars" (now known as novae or supernovae), in particular that of 1572, lacked the parallax expected in sub-lunar phenomenon, and were therefore not "atmospheric" tail-less comets as previously believed, but occurred above the atmosphere and moon. Using similar measurements he showed that comets were also not atmospheric phenomena, as previously thought, and must pass through the supposed "immutable" celestial spheres.

Tycho Brahe was granted an estate on the island of Hven and the funding to build the Uraniborg, an early research institute, where he built large astronomical instruments and took many careful measurements, and later Stjerneborg, underground, when he discovered that his instruments in the former were not sufficiently steady. Something of an autocrat on the island he nevertheless founded manufactories such as paper-making to provide material for printing his results. Something akin to a research institute was founded which John Napier attended. After disagreements with the new Danish king in 1597, he was invited by the Bohemian king and Holy Roman emperor Rudolph II to Prague, where he became the official imperial astronomer. He built the new observatory at Benátky nad Jizerou. Here, from 1600 until his death in 1601, he was assisted by Johannes Kepler. Kepler later used Tycho's astronomical results to develop his own theories of astronomy.

As an astronomer, Tycho worked to combine what he saw as the geometrical benefits of the Copernican system with the philosophical benefits of the Ptolemaic system into his own model of the universe, the Tychonic system.

Tycho is credited with the most accurate astronomical observations of his time, and the data were used by his assistant, Johannes Kepler, to derive the laws of planetary motion. No one before Tycho had attempted to make so many planetary observations.

love playing with kids and the willys

Career: observing the heavens

The 1572 supernova

File:Main tycho remnant full.jpg

Composite image of Tycho's supernova from observations with Chandra, Spitzer and the Calar Alto Observatory, imaged more than four centuries after its discovery

On 11 November 1572, Tycho observed (from Herrevad Abbey) a very bright star, now named SN 1572, which had unexpectedly appeared in the constellation Cassiopeia. Because it had been maintained since antiquity that the world beyond the Moon's orbit was eternally unchangeable (celestial immutability was a fundamental axiom of the Aristotelian world-view), other observers held that the phenomenon was something in the terrestrial sphere below the Moon. However, in the first instance Tycho observed that the object showed no daily parallax against the background of the fixed stars. This implied it was at least farther away than the Moon and those planets that do show such parallax. He also found the object did not change its position relative to the fixed stars over several months as all planets did in their periodic orbital motions, even the outer planets for which no daily parallax was detectable. This suggested it was not even a planet, but a fixed star in the stellar sphere beyond all the planets. In 1573 he published a small book, De nova stella thereby coining the term nova for a "new" star (we now classify this star as a supernova and we know that it is 7500 light-years from Earth). This discovery was decisive for his choice of astronomy as a profession. Tycho was strongly critical of those who dismissed the implications of the astronomical appearance, writing in the preface to De nova stella: "O crassa ingenia. O caecos coeli spectatores" ("Oh thick wits. Oh blind watchers of the sky").

Tycho's discovery was the inspiration for Edgar Allan Poe's poem, "Al Aaraaf". In 1998, Sky & Telescope magazine published an article by Donald W. Olson, Marilynn S. Olson and Russell L. Doescher arguing, in part, that Tycho's supernova was also the same "star that's westward from the pole" in Shakespeare's Hamlet.

Tycho's observatories

Watercolor plan of Uraniborg

In 1574, Tycho published the observations made in 1572 from his first observatory at Herrevad Abbey. He then started lecturing on astronomy, but gave it up and left Denmark in spring 1575 to tour abroad. He first visited William IV, Landgrave of Hesse-Kassel's observatory at Kassel, then went on to Frankfurt, Basel and Venice. Upon his return he intended to relocate to Basel, but King Frederick II of Denmark, desiring to keep the distinguished scientist, offered Tycho the island of Hven in Oresund and funding to set up an observatory. Tycho first built Uraniborg in 1576 (with a laboratory for his alchemical experiments in its cellar) and then Stjerneborg in 1581. Unusual for the time, Tycho established Uraniborg as a research centre, where almost 100 students and artisans worked from 1576 to 1597.

After Frederick died in 1588 and his 11-year old son, Christian IV, succeeded him, Tycho's influence steadily declined. After several unpleasant disagreements, Tycho left Hven in 1597.

He moved to Prague in 1599. Sponsored by Rudolf II, Holy Roman Emperor, Tycho built a new observatory in a castle in Benátky nad Jizerou, 50 km from Prague, and worked there for one year. The emperor then brought him back to Prague, where he stayed until his death. Tycho received financial support from several nobles in addition to the emperor, including Oldrich Desiderius Pruskowsky von Pruskow, to whom he dedicated his famous "Mechanica". In return for their support, Tycho's duties included preparing astrological charts and predictions for his patrons on events such as births, weather forecasting, and astrological interpretations of significant astronomical events, such as the supernova of 1572 (sometimes called Tycho's supernova) and the Great Comet of 1577.

Tycho's observational astronomy

Mural quadrant (Tycho Brahe 1598)

Tycho's observations of stellar and planetary positions were noteworthy both for their accuracy and quantity. His celestial positions were much more accurate than those of any predecessor or contemporary. Rawlins (1993, §B2) asserts of Tycho's Star Catalog D, "In it, Tycho achieved, on a mass scale, a precision far beyond that of earlier catalogers. Cat D represents an unprecedented confluence of skills: instrumental, observational, & computational—all of which combined to enable Tycho to place most of his hundreds of recorded stars to an accuracy of ordermag 1'!"

He aspired to a level of accuracy in his estimated positions of celestial bodies of being consistently within 1 arcminute of their real celestial locations, and also claimed to have achieved this level. But in fact many of the stellar positions in his star catalogues were less accurate than that. The median errors for the stellar positions in his final published catalog were about 1'.5, indicating that only half of the entries were more accurate than that, with an overall mean error in each coordinate of around 2'. Although the stellar observations as recorded in his observational logs were more accurate, varying from 32.3" to 48.8" for different instruments, systematic errors of as much as 3' were introduced into some of the stellar positions Tycho published in his star catalog due, for instance, to his application of an erroneous ancient value of parallax and his neglect of polestar refraction. Incorrect transcription in the final published star catalogue, by scribes in Brahe's employ, was the source of even larger errors, sometimes by many degrees.

After his death, his records of the motion of the planet Mars provided evidence to support Kepler's discovery of the ellipse and area laws of planetary motion. Kepler's application of these two laws to obtain astronomical tables of unprecedented accuracy (the Rudolphine Tables) provided powerful support for his heliocentric model of the solar system.

Tycho himself was not a Copernican, but proposed a system in which the Sun and Moon orbited the Earth, while the other planets orbited the Sun. His system provided a safe position for astronomers who were dissatisfied with older models but were reluctant to accept the Earth's motion. It gained a considerable following after 1616 when Rome decided officially that the heliocentric model was contrary to both philosophy and Scripture, and could be discussed only as a computational convenience that had no connection to fact. His system also offered a major innovation: while both the geocentric model and the heliocentric model as set forth by Copernicus relied on the idea of transparent rotating crystalline spheres to carry the planets in their orbits, Tycho eliminated the spheres entirely.

Celestial objects observed near the horizon and above appear with a greater altitude than the real one, due to atmospheric refraction, and one of Tycho's most important innovations was that he worked out and published the very first tables for the systematic correction of this possible source of error. But as advanced as they were, they attributed no refraction whatever above 45 degrees altitude for solar refraction, and none for starlight above 20 degrees altitude.

To perform the huge number of multiplications needed to produce much of his astronomical data, Tycho relied heavily on the then-new technique of prosthaphaeresis, an algorithm for approximating products based on trigonometric identities that predated logarithms.

Tycho's geo-heliocentric astronomy

Main article: Tychonic system

In this depiction of the Tychonic system, the objects on blue orbits (the Moon and the Sun) revolve around the Earth. The objects on orange orbits (Mercury, Venus, Mars, Jupiter, and Saturn) revolve around the Sun. Around all is a sphere of fixed stars.

Valentin Naboth's drawing of Martianus Capella's geo-heliocentric astronomical model (1573)

Kepler tried, but was unable, to persuade Tycho to adopt the heliocentric model of the solar system. Tycho believed in geocentrism because he held the Earth was just too sluggish to be continuously in motion and also believed that if the Earth orbited the Sun annually there should be an observable stellar parallax over any period of six months, during which the angular orientation of a given star would change. This parallax does exist, but is so small it was not detected until the 1830s, when Friedrich Bessel discovered a stellar parallax of 0.314 arcseconds of the star 61 Cygni in 1838. Tycho advocated an alternative to the Ptolemaic geocentric system, a geo-heliocentric system now known as the Tychonic system. In such a system, the Sun annually circles a central Earth (regarded as essentially different from the planets), while the five planets orbit the Sun.

Tycho was not the first to propose a geoheliocentric system. It used to be thought that Heraclides in the 4th century BC had suggested that Mercury and Venus revolve around the Sun, which in turn (along with the other planets) revolves around the Earth. Ambrosius Theodosius Macrobius (395–423 AD) later described this as the "Egyptian System," stating that "it did not escape the skill of the Egyptians," though there is no other evidence it was known in ancient Egypt. The difference was that Tycho's system had all the planets (with the exception of Earth) revolving around the Sun, instead of just the interior planets of Mercury and Venus. In this regard, he was anticipated in the 15th century by the Kerala school astronomer Nilakantha Somayaji, whose geoheliocentric system also had all the planets revolving around the Sun. The difference to both these systems was that Tycho's model of the Earth does not rotate daily, as Heraclides and Nilakantha claimed, but is static.

Another crucial difference between Tycho's 1587 geo-heliocentric model and those of other geo-heliocentric astronomers, such as Paul Wittich, Reimarus Ursus, Helisaeus Roeslin and David Origanus, was that the orbits of Mars and the Sun intersected. This was because Tycho had come to believe the distance of Mars from the Earth at opposition (that is, when Mars is on the opposite side of the sky from the Sun) was less than that of the Sun from the Earth. Tycho believed this because he came to believe Mars had a greater daily parallax than the Sun. But in 1584 in a letter to a fellow astronomer, Brucaeus, he had claimed that Mars had been further than the Sun at the opposition of 1582, because he had observed that Mars had little or no daily parallax. He said he had therefore rejected Copernicus's model because it predicted Mars would be at only two-thirds the distance of the Sun. But he apparently later changed his mind to the opinion that Mars at opposition was indeed nearer the Earth than the Sun was, but apparently without any valid observational evidence in any discernible Martian parallax. Such intersecting Martian and solar orbits meant that there could be no solid rotating celestial spheres, because they could not possibly interpenetrate. Arguably this conclusion was independently supported by the conclusion that the comet of 1577 was superlunary, because it showed less daily parallax than the Moon and thus must pass through any celestial spheres in its transit.

Tychonic astronomy after Tycho

Galileo's 1610 telescopic discovery that Venus shows a full set of phases refuted the pure geocentric Ptolemaic model. After that it seems 17th century astronomy then mostly converted to geo-heliocentric planetary models that could explain these phases just as well as the heliocentric model could, but without the latter's disadvantage of the failure to detect any annual stellar parallax that Tycho and others regarded as refuting it. The three main geo-heliocentric models were the Tychonic, the Capellan with just Mercury and Venus orbiting the Sun such as favoured by Francis Bacon, for example, and the extended Capellan model of Riccioli with Mars also orbiting the Sun whilst Saturn and Jupiter orbit the fixed Earth. But the Tychonic model was probably the most popular, albeit probably in what was known as 'the semi-Tychonic' version with a daily rotating Earth. This model was advocated by Tycho's ex-assistant and disciple Longomontanus in his 1622 Astronomia Danica that was the intended completion of Tycho's planetary model with his observational data, and which was regarded as the canonical statement of the complete Tychonic planetary system.

A conversion of astronomers to geo-rotational geo-heliocentric models with a daily rotating Earth such as that of Longomontanus may have been precipitated by Francesco Sizzi's 1613 discovery of annually periodic seasonal variations of sunspot trajectories across the sun's disc. They appear to oscillate above and below its apparent equator over the course of the four seasons. This seasonal variation is explained much better by the hypothesis of a daily rotating Earth together with that of the sun's axis being tilted throughout its supposed annual orbit than by that of a daily orbiting sun, if not even refuting the latter hypothesis because it predicts a daily vertical oscillation of a sunspot's position, contrary to observation. This discovery and its import for heliocentrism, but not for geo-heliocentrism, is discussed in the Third Day of Galileo's 1632 Dialogo. However, prior to that discovery, in the late 16th century the geo-heliocentric models of Ursus and Roslin had featured a daily rotating Earth, unlike Tycho's geo-static model, as indeed had that of Heraclides in antiquity, for whatever reason.

The fact that Longomontanus's book was republished in two later editions in 1640 and 1663 no doubt reflected the popularity of Tychonic astronomy in the 17th century. Its adherents included John Donne and the atomist and astronomer Pierre Gassendi.

Johannes Kepler published the Rudolphine Tables containing a star catalog and planetary tables using Tycho's measurements. Hven island appears west uppermost on the base.

The ardent anti-heliocentric French astronomer Jean-Baptiste Morin devised a Tychonic planetary model with elliptical orbits published in 1650 in a simplified, Tychonic version of the Rudolphine Tables. Some acceptance of the Tychonic system persisted through the 17th century and in places until the early 18th century; it was supported (after a 1633 decree about the Copernican controversy) by "a flood of pro-Tycho literature" of Jesuit origin. Among pro-Tycho Jesuits, Ignace Pardies declared in 1691 that it was still the commonly accepted system, and Francesco Blanchinus reiterated that as late as 1728. Persistence of the Tychonic system, especially in Catholic countries, has been attributed to its satisfaction of a need (relative to Catholic doctrine) for "a safe synthesis of ancient and modern". After 1670, even many Jesuit writers only thinly disguised their Copernicanism. But in Germany, Holland, and England, the Tychonic system "vanished from the literature much earlier".

James Bradley's discovery of stellar aberration, published 1729, eventually gave direct evidence excluding the possibility of all forms of geocentrism including Tycho's. Stellar aberration could only be satisfactorily explained on the basis that the Earth is in annual orbit around the Sun, with an orbital velocity that combines with the finite speed of the light coming from an observed star or planet, to affect the apparent direction of the body observed.

Tycho's lunar theory

Tycho's distinctive contributions to lunar theory include his discovery of the Variation of the Moon's longitude. This represents the largest inequality of longitude after the equation of the center and the evection. He also discovered librations in the inclination of the plane of the lunar orbit, relative to the ecliptic (which is not a constant of about 5° as had been believed before him, but fluctuates through a range of over a quarter of a degree), and accompanying oscillations in the longitude of the lunar node. These represent perturbations in the Moon's ecliptic latitude. Tycho's lunar theory doubled the number of distinct lunar inequalities, relative to those anciently known, and reduced the discrepancies of lunar theory to about 1/5 of their previous amounts. It was published posthumously by Kepler in 1602, and Kepler's own derivative form appears in Kepler's Rudolphine Tables of 1627.

Legacy

Although Tycho's planetary model was soon discredited, his astronomical observations were an essential contribution to the scientific revolution. The traditional view of Tycho is that he was primarily an empiricist who set new standards for precise and objective measurements. This appraisal originated in Pierre Gassendi's 1654 biography, Tychonis Brahe, equitis Dani, astronomorum coryphaei, vita. It was furthered by Johann Dreyer's biography in 1890, which was long the most influential work on Tycho. According to historian of science Helge Kragh, this assessment grew out of Gassendi's opposition to Aristotelianism and Cartesianism, and fails to account for the diversity of Tycho's activities.

Tycho considered astrology to be a subject of great importance. In addition to his contributions to astronomy, he was famous in his own time also for his contributions to medicine; his herbal medicines were in use as late as the 1900s. Although the research community Tycho created in Uraniborg did not survive him, while it existed it was both a research center and an institution of education, functioning as a graduate school for Danish and foreign students in both astronomy and medicine. Tycho's success as a scientist also depended on his adroit political skills, to obtain patronage and funding for his work.

The crater Tycho on the Moon is named after him, as is the crater Tycho Brahe on Mars. The Tycho Brahe Planetarium in Copenhagen is also named after him.

HEAT1X-TYCHO BRAHE is the name of a manned private spacecraft to be launched by Copenhagen Suborbitals. Other things named after him include a bar in Zagreb and a ferry operating between Sweden and Denmark. Tycho Brahe is also the alias of one of the main characters of Penny Arcade.

See also

• December 1573 lunar eclipse
• History of trigonometry
• Regiomontanus

References

Opera omnia

• Brahe, Tycho. Tychonis Brahe Dani Opera Omnia (in Latin). 15 vols. 1913–1929. Edited by J. L. E. Dreyer.
• Brahe, Tycho. 'Astronomiæ instauratæ mechanica', 1598 European Digital Library Treasure
• Bricka, Carl Frederik, Dansk Biografisk Lexikon, vol. II [Beccau - Brandis], 1888. Online edition
• Cowen, R. (18 December 1999). "Danish astronomer argues for a changing cosmos". Science News. 156 (25 & 26). Archived from the original on 2005-08-28. Retrieved 2008-07-28.
• Dreyer, John Louis Emil (2004) [1890]. Tycho Brahe: A Picture of Scientific Life and Work in the Sixteenth Century. Kessinger Publishing. ISBN 978-0766185296. OCLC 70058046.
• Gingerich, Owen (1989). Johannes Kepler. In Taton&Wilson (1989, pp.54-78).
• Hoskin, M. (ed.) The Cambridge Concise History of Astronomy CUP 1999
• Kragh, Helge (2005). Fra Middelalderlærdom til Den Nye Videnskab. Dansk Naturvidenskabs Historie (in Danish). Vol. 1. Aarhus: Aarhus Universitetsforlag. ISBN 87-7934-168-3.
• Linton, Christopher M. (2004). From Eudoxus to Einstein—A History of Mathematical Astronomy. Cambridge: Cambridge University Press. ISBN 978-0-521-82750-8.
• Olson, Donald W.; Olson, Marilynn S.; Doescher, Russell L., "The Stars of Hamlet," Sky & Telescope (November 1998)
• Pannekoek, A. A History of Astronomy Allen & Unwin 1961
• Pledge, H. Science since 1500 1939
• Rawlins, Dennis (October 1993). "Tycho's 1004 Star Catalog" (PDF). DIO, the International Journal of Scientific History. 3 (1). Retrieved 2009-10-25.
• Rybka, P. Katalog Gwiazdowy Heweliusza, Warsaw 1984.
• Skautrup, Peter, 1941 Den jyske lov: Text med oversattelse og ordbog. Aarhus: Universitets-forlag.
• Stephenson, Bruce (1987). Kepler's physical astronomy. Princeton University Press. ISBN 0-691-03652-7. Retrieved 2009-10-10.
• Swerdlow, Noel M. (2004). "An Essay on Thomas Kuhn's First Scientific Revolution, The Copernican Revolution" (PDF). Proceedings, American Philosophical Society. 48 (1): 64–120. Retrieved 2009-10-10.
• Swerdlow, N. M. Astronomy in the Renaissance in Walker 1996
• Taton, René; Wilson, Curtis, eds. (1989). Planetary astronomy from the Renaissance to the rise of astrophysics Part A: Tycho Brahe to Newton. Cambridge: Cambridge University Press. ISBN 0-521-24254-1. Retrieved 2009-11-06.
• Thoren, Victor E.; Christianson, John Robert (1990). The Lord of Uraniborg: a biography of Tycho Brahe. Cambridge University Press. ISBN 0-521-35158-8.
• Thoren, V. Tycho Brahe in Taton & Wilson CUP 1989
• Walker, C. (ed.) Astronomy before the telescope British Museum Press 1996
• Wesley, W. G. "The Accuracy of Tycho Brahe's Instruments," Journal for the History of Astronomy, 9 (1978)
• Wittendorff, Alex. 1994. Tyge Brahe. Copenhagen: G. E. C. Gad.
• "Strange Cases from the Files of Astronomical Sociology". University of Notre Dame. Archived from the original on 2008-02-05. Retrieved 31 March 2005.

Further reading

• John Robert Christianson (2000). On Tycho's Island: Tycho Brahe and his assistants, 1570–1601. Cambridge University Press. ISBN 0-521-65081-X.
• John Robert Christianson (2002). On Tycho's Island: Tycho Brahe, science, and culture in the sixteenth century. Cambridge University Press. ISBN 0-521-00884-0.
• Kitty Ferguson: The nobleman and his housedog: Tycho Brahe and Johannes Kepler: the strange partnership that revolutionised science. London: Review, 2002 ISBN 0-7472-7022-8 (published in the US as: Tycho & Kepler: the unlikely partnership that forever changed our understanding of the heavens. New York: Walker, 2002 ISBN 0-8027-1390-4)
• Joshua Gilder and Anne-Lee Gilder Heavenly intrigue. New York: Doubleday, 2004 ISBN 0-385-50844-1
• Arthur Koestler: The Sleepwalkers: A History of Man's Changing Vision of the Universe. Hutchinson, 1959; reprinted in Arkana, 1989
• Godfred Hartmann. Urania. Om mennesket Tyge Brahe. Copenhagen: Gyldendal, 1989 ISBN 87-00-62763-1
• Wilson & Taton. Planetary astronomy from the Renaissance to the rise of astrophysics 1989 CUP (articles by Thoren, Jarell and Schofield on the nature and history of the Tychonic astronomical model)
• Wesley, Walter G. (1978). "The Accuracy of Tycho Brahe's Instruments" (PDF). Journal for the History of Astronomy. 9: 42–53. Bibcode:1978JHA.....9...42W. Retrieved 2009-09-24. (analysis of individual instrument accuracies)
• Rawlins, Dennis (1993). "Tycho's 1004-­Star Catalog / The First Critical Edition" (PDF). 3. The International Journal of Scientific History. ISSN 1041-5440. Retrieved 2009-09-24. {{cite journal}}: Cite journal requires |journal= (help); Unknown parameter |month= ignored (help); soft hyphen character in |title= at position 14 (help) (critical analysis of Tycho's 1004 star catalogue D. Printing date: 2009\1\12)

External links

• The opening of Tycho Brahe's tomb Aarhus University.
• Tycho Brahe Homepage
• Brahe, Tycho MacTutor History of Mathematics
• Tycho Brahe pages by Adam Mosley at Starry Messenger: An Electronic History of Astronomy, University of Cambridge
• The Noble Dane: Images of Tycho Brahe. The Museum of the History of Science, Oxford, exhibits Eduard Ender's painting and other Tycho material.
• Astronomiae instauratae mechanica, 1602 edition - Full digital facsimile, Lehigh University.
• Astronomiae instauratae mechanica, 1602 edition - Full digital facsimile, Smithsonian Institution.
• Astronomiae instauratae mechanica, 1598 edition - Full digital facsimile, the Danish Royal Library. Includes Danish and English translations.
• Electronic facsimile editions of the rare book collection at the Vienna Institute of Astronomy
• Brahe Bio at Skyscript
• The Galileo Project article on Tycho Brahe
• The Observations of Tycho Brahe
• Learned Tico Brahae, His Astronomicall Coniectur, 1632 - Full digital facsimile, Linda Hall Library.
• The play Rudolf II, by Edward Einhorn, features Tycho Brahe as a character
• Tycho Brahe: the master of naked eye astronomy - background and hands on activities
• Coat-of-arms of Tycho Brahe
• Tycho Brahe museum, Ven, Sweden