The Correspondence of Tycho Brahe (505 letters)

Primary Contributors:

Adam Mosley

Portrait of Tycho Brahe, from the title page of his Astronomiae Instauratae Mechanica (Nuremberg: Apud Levinum Hulsium, 1602); image courtesy of the Whipple Library, University of Cambridge.

Tycho Brahe (1546–1601)

Born at Knutstorp Castle, in what is now part of Sweden, to an aristocratic Danish family, Tycho Brahe was always destined for an illustrious career. But from an early age he displayed a greater interest in studying the heavens than in preparing to take up a position at court. After three years at the University of Copenhagen, he spent much of the period from 1562 to 1576 travelling, spending time at the Universities of Leipzig, Wittenberg, and Rostock, and working with other scholars in Basel, Augsburg, and Kassel. It was in Rostock in 1566 that he lost part of his nose in a duel; subsequently he wore a prosthesis.

The appearance in 1572 of a ‘new star’ (a supernova), prompted Brahe’s first publication, De nova stella, and in 1574 he was invited to deliver a course of lectures on astronomy at the University of Copenhagen. In 1576, King Frederick II of Denmark awarded him the fiefdom of Hven, an island in the Danish Sound, as a site at which to pursue his studies. With generous royal support, Brahe constructed on Hven a domicile and observatory, which he called Uraniborg, and developed a range of astronomical instruments of remarkable size and accuracy. Brahe worked at Uraniborg, pursuing alchemy as well as astronomy, with the help of a team of assistants, for more than twenty years. But in 1597, after King Christian IV’s attainment of his majority led to a decline in Brahe’s funding and standing, he left Denmark in search of new patronage. In 1599 he settled near Prague, having been appointed Imperial Mathematician by Emperor Rudolf II; Johannes Kepler joined him there as an assistant the following year.

Brahe began several publications on Hven, where he installed his own printing press and constructed a paper mill to supply it. His works include De mundi aethereis recentioribus phaenomenis (1588), which discussed the comet of 1577 and presented his geoheliocentric alternative to the world-systems of Ptolemy and Copernicus; the Astronomiae instauratae mechanica (1598), an illustrated account of his observatory and observing apparatus; and the Astronomiae instauratae progymnasmata (1602), which contained his theory of lunar and solar motions, part of his catalogue of stars, and further analysis of the supernova of 1572. The latter work was completed posthumously, but even those books which were distributed in Brahe’s lifetime were mostly disseminated privately and non-commercially, despite the large print-runs he usually preferred. Later commercial ‘editions’ of his works incorporated many of the sheets from his printshop.

Given the limited distribution of his printed works, correspondence with other scholars was thus an important mechanism by which Brahe communicated his results, became known to others, and managed his scholarly reputation. His letters were also used to acquire astronomical data, collaborate with others, and conduct disputes over priority and credit. In common with many scholars of the period, Brahe circulated some of his correspondence with a wider audience in manuscript. But Brahe also acknowledged the significance of letters for his astronomical enterprise by publishing the letters he exchanged with Landgrave Wilhelm IV of Hessen-Kassel and the Landgrave’s astronomer, Christoph Rothmann, as the Epistolarum astronomicarum liber primus (1596); as this title suggests, further volumes of astronomical letters, exchanged with other correspondents, were planned and begun, but remained unfinished at Brahe’s death in 1601.

Partners and Additional Contributors

The metadata was supplied to Cultures of Knowledge by Professor Adam Mosley of Swansea University who collated it from the Opera omnia in the course of his research. Cultures of Knowledge would like to thank EMLO Digital Fellow Rose Hedley for her assistance with the preparatory work prior to upload.

Key Bibliographic Source(s)

Tychonis Brahe Dani Opera omnia, ed. J. L. E. Dreyer, 15 vols (Copenhagen, 1913–1929).


The letters included in this catalogue range in date from January 1568 to July 1601, just a couple of months before Tycho Brahe’s death. Written, for the most part, in Latin, they include 278 letters written by Brahe, and 190 letters addressed to him, and involve a total of 144 correspondents scattered the length and breadth of Europe. Brahe’s scholarly correspondents included Johannes Kepler, Michael Maestlin, Joseph Scaliger, Giovanni Antonio Magini, Caspar Peucer, and Thaddaeus Hagecius. His letters often touch upon his and others’ astronomical observations; upon the correct interpretation of novae and comets; on the relative merits of the Ptolemaic, Copernican, and Tychonic world-systems; upon the acquisition of books on these and other topics; on his publication programme and the resources needed to complete it; and on his disputes with various adversaries. The letters rarely touch upon his alchemical beliefs and practices. Brahe also exchanged letters with numerous aristocrats and princes; many of these relate to his search for new patronage after he left Denmark and his attempt to secure printing privileges for his publications. Along with the inscriptions in extant presentation copies, the correspondence provides evidence of the private distribution of his printed publications and circulation of manuscript materials (including letters).

Letters in the catalogue appear under their original date. For letters written after the Gregorian calendrical reform, it is indicated, whenever known, whether this date provided is Julian or Gregorian.

Detail of Tycho’s signature, 1598. (Manuscript from the Waller Collection, Uppsala universitetsbibliotek; image from Wikimedia Commons.)


Catalogue entries derive from, and refer to, the letters as published in the Tychonis Brahe Dani Opera omnia, 15 volumes, first published between 1913 and 1929, under the editorial oversight of J. L. E. Dreyer. The majority of Brahe’s letters appear in volume 6 (reproducing the Epistolarum astronomicarum liber primus), volume 7, and volume 8. Some come from volume 14, devoted to documents pertaining to Brahe’s life. A few, included by Brahe in other works, are to be found in volumes 1–5, which reproduce those publications.

Dreyer’s editorial work has generally stood the test of time and the critical scrutiny of later Brahe scholars. In addition to reproducing and annotating letters as printed by Brahe, he studied and meticulously recorded the existence of manuscript versions, when available, in libraries and archives in Copenhagen, Vienna, Marburg, and other locations. Users of the Opera omnia should be aware, however, that variants and errata can be found in volume 9 as well as in the Latin endnotes to each of the volumes referenced.

Scholars working with Brahe’s letters may wish to consult also those published, with their own apparatus, in the works and letters of his correspondents: e.g. Johannes Kepler Gesammelte Werke and The Correspondence of Joseph Scaliger (the metadata for which may be found in EMLO’s Scaliger catalogue).

Scope of Catalogue

For each letter, a bibliographic reference to the printed copy in Tychonis Brahe Dani Opera omnia has been provided, together with volume number, and a link given to the copy in the scanned edition mounted on The Internet Archive whenever the relevant volume is available for consultation. Some documents unknown to Dreyer have emerged since 1929; these include some letters published by Wilhelm Norlind in Tycho Brahe: En levnadsteckning med nya bidrag belysande hans liv och verk (Lund: CWK Gleerup, 1970), pp. 366–82, and some Danish letters reproduced in John Robert Christianson, ‘Addenda to Tychonis Brahe Opera Omnia tomus XIV’, Centaurus, 16 (1972), pp. 231–47.

Further resources


Tychonis Brahe Dani Opera omnia, ed. J. L. E. Dreyer, 15 vols (Copenhagen, 1913–1929).

John Robert Christianson, ‘Addenda to Tychonis Brahe Opera Omnia tomus XIV’, Centaurus, 16 (1972), pp. 231–47.

John Robert Christianson, On Tycho’s Island: Tycho Brahe and His Assistants, 1570–1601 (Cambridge, 2000).

J. L. E. Dreyer, Tycho Brahe: A Picture of Scientific Life and Work in the Sixteenth Century (Edinburgh: Adam & Charles Black, 1890).

Adam Mosley, Nicholas Jardine, and Karin Tybjerg, ‘Epistolary culture, editorial practices, and the propriety of Tycho’s Astronomical Letters’, Journal for the History of Astronomy, 34 (2003), pp. 421–51.

Adam Mosley, Bearing the Heavens. Tycho Brahe and the Astronomical Community of the Late Sixteenth Century (Cambridge, 2007).

Wilhelm Norlind, Tycho Brahe: En levnadsteckning med nya bidrag belysande hans liv och verk (Lund: C.W.K. Gleerup, 1970).

Victor E. Thoren, The Lord of Uraniborg: A Biography of Tycho Brahe (Cambridge: Cambridge University Press, 1990).

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