The Milky Way in Johann Bayer's Uranometria,1603

Warner Deborah J. , “Johann Bayer and his star atlas – reconsidered”, Journal of the British Astronomical Association, lxxxvi (1975), 53–4. Before Bayer, at most Galluci's Theatrum mundi et temporis was sufficient to meet the scientific demand, because its plates already contained angular scales from which the stars’ positions could be read off (according to: Jürgen Hamel, Die Himmelsvermessung des Johannes Bayer: Begleitbuch zur Uranometria von Johann Bayer 1603 (Gerchsheim, 2010), 32–3). As early as 1821, Jean-Baptiste Joseph Delambre offered criticism of the accuracy: “L'ouvrage et l'explication sont également médiocres” (J. B. Delambre, Histoire de l'astronomie moderne, ii (Paris, 1821), 185). In 1842, Friedrich Wilhelm Argelander proved the overall inconsistency of the data quality in his dissertation, De fide Uranometriae Bayeri dissertatio academica (Bonn, 1842).

Hamel , op. cit. (ref. 1), 68. This is a companion book to a very fine and accurate facsimile reprint of the Uranometria.

Apart from the fact that nothing is known of a corresponding journey, Bayer's use of Keyser's catalogue of southern stars instead of his own observational results virtually disproves this hypothesis. Additionally, the southern Milky Way as depicted in the Uranometria deviates rather obviously from the ‘real’ visual picture as recorded for example by Pannekoek (Antonin Pannekoek, “Die südliche Milchstraße”, Annalen van de Bosscha-Sterrewacht, ii/1 (Lembang, 1928), A61-A63).

In the Uranometria, the Milky Way spans the following constellation plates: Plate 3 (Draco), 4 (Cepheus), 7 (Hercules), 8 (Lyra), 9 (Cygnus), 10 (Cassiopeia), 11 (Perseus), 12 (Auriga), 13 (Ophiuchus), 14 (Serpens), 15 (Sagitta), 16 (Aquila and Antinous), 17 (Delphinus), 20 (Andromeda), 23 (Taurus), 24 (Gemini), 29 (Scorpius), 30 (Sagittarius), 35 (Orion), 36 (Eridanus), 38 (Canis Major), 39 (Canis Minor), 40 (Argo), 41 (Centaurus), 44 (Hydra), 45 (Lupus), 46 (Ara), 47 (Corona Australis), 49 (Coelum Australis) together with the two hemispheric plates (50 and 51). Thus the Milky Way is shown on 31 plates in total. Some regions are displayed on more than one plate.

A possible exception can be found on Plate 16 (Aquila): the Milky Way west of Antinous (area of the modern constellation Scutum) shows a somewhat increased density of the dots of which the shading of the Milky Way is compounded, possibly indicating a bright Milky Way feature. Indeed the position fits the real Milky Way almost perfectly: The ‘Scutum Cloud’, which is located in precisely this area, is known to be one of the brightest portions of the Northern Milky Way. However, the feature, as displayed in the Uranometria, is rather inconspicuous, and a mere coincidence regarding a random fluctuation, accidentally introduced by the artist, cannot be ruled out.

The first drawing of the southern Milky Way showing internal structure was published by James Dunlop in 1828 ( Dunlop James . “A catalogue of nebulae and clusters of stars in the southern hemisphere, observed at Paramatta in New South Wales”, in Philosophical transactions of the Royal Society of London, cxviii (1828), 113–51). Only in 1872 did Eduard Heis publish a visual representation of the Milky Way down to −20° of declination, in his Atlas coelestis novus (Cologne, 1872), which contained an inner structure equivalent to the varying surface brightness of of the Milky Way. A historiographic overview of visual representations of the Milky Way up to the year 1893 can be found in the foreword to Cornelis Easton's La voie lactée dans l'hémisphère boréal (Paris, 1893).

Swerdlow Noel M. , “A star catalogue used by Johannes Bayer”, Journal for the history of astronomy, xvii (1986), 189–97, p. 189.

Swerdlow , op. cit. (ref. 7), 192.

Warner Deborah J. , The sky explored (Amsterdam, 1979), 18–19.

Dekker Elly , Illustrating the phaenomena (Oxford, 2013), 77–8.

Dekker quotes the descriptions in Manilius's Astronomica and — historically even more influential — the data contained in Hyginus's work De astronomica, Books III and IV, as the most important sources.

An extensive study of this magnificent globe, its data and the persons having been granted access to it, can be found in Mosley Adam , Bearing the heavens (Cambridge, 2007).

Brahe Tycho , Astronomiae instauratae mechanica (Nuremberg, 1602), 80.

Brahe Tycho , Astronomiae instauratae progymnasmata (Frankfurt, 1610).

van der Krogt Peter , Globi Neerlandici (Utrecht, 1993), 106. This can be concluded from an inscription on the 1594 globe: “Jacobus Florentinus / civis Amstelredamensis / hunc Caelestum Globum missio in daniam filio / suo Henrico qui Stellas ex / verificatis observationibus / Nobilis Viri / Tychonis Brahe / appositè designaret, confieri / curavit: Eodem Domino / Tychone privilegia sibi concessa illi benignè / impartiente / 1594”. See also Reinhard Glasemann, Erde Sonne Mond & Sterne (Frankfurt am Main, 1999), 16, and also John Robert Christianson, On Tycho's island (Cambridge, 2003). The stay of the van Langren sons at Uraniborg is thematized by Mosley, op. cit. (ref. 12), 232.

The conclusion that Tycho's Globus magnus did, at best, show the Almagest Milky Way is strongly supported by an analysis of Johannes Kepler's study on the supernova of 1604, De stella nova in pede Serpentarii (Prague, 1606). In the accompanying star map, which mainly shows the constellation of Ophiuchus, one can easily trace the Milky Way, and again it is the Almagest version — a fact that is not surprising: Kepler explicitly referenced the Almagest description of the Milky Way. This is all the more significant as Kepler, being Tycho's administrator, had access to all of his original data records, a fact that he emphasizes in his text.

Brahe Tycho , op. cit. (ref. 14), 231.

Brahe Tycho , op. cit. (ref. 13), 80.

Schöner Johannes . Opera mathematica Ioannis Schoeneri Carolostadii in unum volumen congesta (Nuremberg, 1551), 642.

The two planispheres are regarded as the first printed visual representations of the celestial sphere of the modern age (Warner, op. cit. (ref. 9), 71). The Milky Way is traceable on both of them, and contrary to recent opinions (lately expressed by Hamel, op. cit. (ref. 1)), its outlines (at least in the northern part) correspond well to the Almagest data. In fact, all substantial structures of Dürer's Milky Way can be traced across most celestial illustrations of the seventeenth century and may well be regarded as the original standard for any ”Almagest-like” Milky Way representation of that era. Even its most significant and specific discrepancy from the Almagest picture — the missing southern part of the western branch of the Milky Way in Scorpius, a peculiarity that already appeared on the template for the planispheres, the Vienna manuscript MS 5415, fol. 168r — was copied by the majority of map makers (but not by Mercator, whose celestial globe of 1551 contains this Milky Way feature).

See ref. 20: the hypothesis that Dürer's and Heinfogel's planispheres were the original standard for later Milky Way illustrations is supported by this fact.

According to Warner, this can be deduced from the fact that the southern stars depicted in the Uranometria had been taken, according to Bayer, from the star catalogue of Pieter Dirkszoon Keyser (op. cit. (ref. 9), 18–19 and 204).

Peter van der Krogt (op. cit. (ref. 15), 152) describes a celestial globe of 1597 (located at the Historisches Museum Lucerne) which was printed using the same copper plates as the lost 1598 globe, and published by Hondius, thus being directly related to the 1598 globe mentioned by Warner. However, Fig. 4.8 in Globi Neerlandici, p. 136, clearly shows the Milky Way representation to be of the Almagest kind, as can be perceived from the course in the Perseus region.

Scans of these gores are available online at http://www.bildindex.de.

Warner Deborah J. . “The first celestial globe of Willem Janszoon Blaeu”, Imago mundi, xxv (1971), 29–38.

van der Krogt Peter , “The history of globe making: A brief overview”, Fine globes and planetaria, 5 November 2002 (Christie's, London, 2002), 9–21.

Christianson , On Tycho's island (ref. 15), 254. See also Warner, op. cit. (ref. 25), 34.

Indeed one can speak of a new “Milky Way standard” having been introduced through Willem Janszoon Blaeu, as most celestial maps and globes published after 1598/1600 seem to favour Blaeu's representation. Undoubtedly, the spread of this new style benefited from its occurrence in the Uranometria.

Stein Johan , “De Hemelglobe van Jodocus Hondius van 1600”, Vereeniging Nederlandsch Historisch Scheepvaart Museum, xiii (1929), 42–7.

Christianson , op. cit. (ref. 27), 235–6 and 247–8.

Hinze Gustav , “Drei Globen des 16. Jahrhunderts”, Bericht des Naturwissenschaftlichen Museums zu Zerbst (Zerbst, 1933), 18–19.

This is independently confirmed by other authors, particularly Gustav Hinze (op. cit. (ref. 32), 162). See also Mosley, op. cit. (ref. 12), 247.

Regiomontanus Johannes . Epytoma Ioannis de Monte Regio in Almagestum Ptolemei (Venice, 1496), 126 (Liber octavus). This passage was left unchanged in the 1543 edition.

Pannekoek Antonin . “Die nördliche Milchstraße”, Annalen van de Sterrewacht te Leiden, xi/3 (1920), 1–115. Plates I-III represent the results of more than 30 years of visually examining the Milky Way.

Quotation after Swerdlow (op. cit. (ref. 7), 189).

The Cassiopeia Milky Way was corrected on Plate 10 (Cassiopeia) and Plate 4 (Cepheus), but was left unchanged on Plates 9 (Cygnus) and 20 (Andromeda). Curiously, the ‘Cassiopeia void’ is completely missing on Plate 3 (Draco), even though the ‘Cepheus arc’ is present. The corrections near α Cygni (Deneb) on Plate 7 surprisingly do not appear on the main Cygnus plate (Plate 9).