J. C. Kapteyn and the Early Twentieth-Century Universe

See, for example, Hoskin M. A. , Stellar astronomy: Historical studies (Chalfont St Giles, Bucks, 1982); Smith R. W. , The expanding universe: Astronomy's ‘Great Debate’, 1900–1931 (Cambridge, 1982); and Berendzen R. Hart R. and Seeley D. , Man discovers the galaxies (New York, 1976). Both Smith and, to a lesser degree, Berendzen have dealt with some issues involving Kapteyn.

For a brief survey of Kapteyn's work, see my “Kapteyn and statistical astronomy”, in van Woerden H. , The Milky Way Galaxy: IAU symposium no. 106 (Dortrecht, 1984), no. 3. A thorough, blow-by-blow analysis of most of the technical issues dealt with in this paper, including a discussion of the immense amount of primary technical literature, may be found in my Seeliger, Kapteyn and the rise of statistical astronomy (unpublished dissertation, Bloomington, Ind., 1976). For a more accessible examination of Seeliger's contributions to our understanding of the stellar universe during this period, see my paper, “H.v. Seeliger and modern stellar astronomy”, Journal for the history of astronomy (forthcoming).

“Bart Bok interview”, American Institute of Physics (15 May 1978), 24.

Among the unsuccessful candidates was Hugo von Seeliger, Kapteyn's lifelong friendly rival; see Peursum-Meijer Schuller tot J. , “De sterrenkunde voor Kapteyn (1614–1878)”, in Blaauw A. , Sterrenkijken Bekeken (Groningen, 1983), 7–31, p. 28.

Kapteyn to Gill D. , 16 December 1885, reprinted in Cape photographic Durchmusterung, i (Annals of the Cape Observatory, iii (1896)), p. xiii (original letter lost). Also see Gill to Kapteyn , 9 January 1885 and 22 January 1886 (Kapteyn Astronomical Laboratory Archives; hereafter: KAL Archives) in which Gill gladly accepts Kapteyn's generous offer of assistance.

Seares F. H. , “J. C. Kapteyn”, Publications of the Astronomical Society of the Pacific [hereafter: PASP], xxxiv (1922), 233–53, p. 233.

I am indebted to Michael Hoskin for bringing this information to my attention, and for clarifying the 61 Cygni episode. See Hoskin , Stellar astronomy (ref. 1), 5–21, espec. p. 9.

Airy G. B. , “On the movement of the solar system”, Memoirs of the Royal Astronomical Society, xxviii (1860), 143–71; and Argelander F. , “Ueber die eigene Bewegung des Sonnensystems”, Astronomische Nachrichten, xvi (1839), cols 43–56.

Safford T. H. , “On the solar motion in space and the stellar distances”, Proceedings of the American Academy of Arts and Sciences, xi (1876), 52–61, p. 55 (second paper).

Hall M. , “The sidereal system”, Memoirs of the Royal Astronomical Society, xliii (1876), 157–97, p. 157.

Safford T. H. , “On certain groups of stars with common proper motions”, Monthly notices of the Royal Astronomical Society [hereafter: MNRAS], xxxviii (1878), 295–7, p. 295. It was generally admitted, however, that in some cases smaller groups of stars did exhibit preferential motions, a tendency at the time called “star-drifting”.

Kapteyn J. C. , “Over de verdeeling van de sterren in de ruimte”, Verslagen en Mededeelingen der Koninklijke Akademie van Wetenschappen te Amsterdam Wis- en Natuurkunde Afdeeling, ix (1892), 418–21; and Monck W.H.S. , “The Sun's motion in space”, PASP, iv (1892), 75–77.

For a survey of the various forms proposed for the ‘mean parallax’ formula, see Robb R. A. , “The correlation between absolute magnitude, linear tangential velocity, distance, apparent magnitude and proper motion”, MNRAS, xcvii (1936), 67–75.

Eddington A. S. , “J. C. Kapteyn”, The observatory, xlv (1922), 261–5, p. 265.

Kapteyn J. C. , “Over de verdeeling der kosmische snelheden”, Verslagen der Zittingen van de Wis- en Natuurkundige Afdeeling der Koniklijke Akademie van Wetenschappen te Amsterdam, iv (1896), 4–18, and “Over de verdeeling der kosmische snelheden”, ibid., vi (1898), 51–60.

Kapteyn J. C. and Kapteyn W. , “On the distribution of cosmic velocities. Part I: Theory”, Groningen publications, v (1900).

Eddington , “J. C. Kapteyn” (ref. 14), 264.

While the first indication that a random distribution did not represent the observed motions of the nearby stars was noted by Kobold H. in “Über die Bewegung im Fixsternsystem”, Astronomische Nachrichten, cxxv (1890), cols 65–72, col. 72, his full analysis was first presented in “Untersuchungen der Eigenbewegung des Auwers-Bradley Catalogs nach der Bessel'schen Methode”, Abhandlungen der Kaiserlicher Leopoldinisch-Carolinischen Deutschen Akademie der Naturforscher, lxiv (1895), 213–365, and subsequent publications.

Kapteyn , “Over de verdeeling der kosmische snelheden” (ref. 15), 57–58, and idem, “The determination of the apex of the solar motion”, Proceedings of the Royal Academy of Amsterdam, ii (1900), 353–62.

Kapteyn to Hale , 23 September 1915 (Hale Microfilm Collection of the Mount Wilson and Las Campanas Observatories, Pasadena, California; hereafter: Hale Microfilm).

Ibid.

Kapteyn J. C. , “Star-streaming”, Report of the British Association for the Advancement of Science, 1905, Section A, 257–65, p. 264. Also see his earlier paper “Statistical methods in stellar astronomy”, International Congress of Arts and Sciences, St Louis, iv (1904), 396–425, espec. pp. 412–22.

Kapteyn , “Star-streaming”, 264.

Kapteyn to Adams Walter S. , 10 December 1910, and Kapteyn to Hale , “Notes”, 17 March 1918 (Hale Microfilm).

Kapteyn to Hale , “Notes”, 17 March 1918 (italics added); also see Kapteyn to Adams W. S. , 11 November 1912 (Hale Microfilm). For the subsequent theoretical studies of star-streaming, see Eddington A. S. , “The systematic motions of the stars”, MNRAS, lxvii (1906), 34–63; and Schwarzschild Karl , “Über die Eigenbewegung der Fixsterne”, Nachrichten von der K. Gesellschaft der Wissenschaften zu Göttingen, (1907), 614–32. Kapteyn first became aware of Eddington's work from Gill; see Gill to Kapteyn , 10 November 1906 (KAL Archives).

Kapteyn's interest in star-streaming always remained very strong. Indeed, in his final attempt at a model of the sidereal system, he explained star-streaming in terms of a gravitational attraction within a rotating system of stars.

Kapteyn to Hale , 13 May 1915, and 6 August 1915 (Hale Microfilm).

Indeed, of the dozen papers Kapteyn published after 1915, six deal with proper motions and parallaxes. For a short time, there was some question about the validity of Kapteyn's parallaxes. Around 1917 Adams and Stromberg, at Mount Wilson, claimed that Kapteyn's proper motions were erroneous. They based their work on the incorrect assumption that there were no giant and dwarf stars, thus suggesting that the distances (mean parallaxes) were much closer. On this episode, see Kapteyn to Hale , 23 May 1918, 6 October 1918, 7 October 1918, and 1 December 1918, and Hale to Kapteyn, 17 August 1918; and Shapley to Hale , 12 September 1920 (Hale Microfilm).

Kapteyn to Hale , 23 September 1915 (Hale Microfilm).

Hale to Kapteyn , 4 November 1915 (Hale Microfilm). In their ensuing correspondence on scientific method, Hale gently recommended that Kapteyn read a number of philosophical works on the subject; Hale to Kapteyn, 22 September 1915, 18 October 1915, and 9 March 1916 (Hale Microfilm).

Hale to Kapteyn , 4 November 1915 (Hale Microfilm).

Kapteyn to Hale , 26 March 1916 (Hale Microfilm). In his letter, Kapteyn noted that he had spoken extensively on the matter of method with “our philosopher Heymans and with Ehrenfest, Lorentz's successor”.

Seeliger presented the detailed results of his investigations in a variety of major papers, published first in 1898, and again in 1909, 1911 and 1912, and finally in 1920, when he presented his last definitive analysis.

Seeliger's first ground-breaking study appeared as “Betrachungen über die räumliche Verteilung der Fixsterne”, Abhandlungen der Mathematisch-Physikalischen Klasse der K. Bayerischen Akademie der Wissenschaften zu München, xix (1898), 565–629. For additional references see supra, ref. 2. For a derivation and solution of Seeliger's “fundamental equation”, see my Seeliger, Kapteyn and the rise of statistical astronomy (ref. 2), 458–67.

See Shapley to Kienle H. , 11 October 1922 (Shapley Archives). Shapley noted that the mathematical abstractness of Seeliger's work hindered many astronomers from understanding Seeliger's contributions better. Also see Kienle to Shapley , 21 September 1922 (Shapley Archives).

Kapteyn J. C. , “On the luminosity of the fixed stars”, Koninklijke Akademie van Wetenschappen te Amsterdam. Proceedings of the section of sciences, iii (1901), 658–89; reprinted with slight corrections in Groningen publications, no. 11 (1902), 3–32.

Ibid., 670; 14.

For a useful analysis of the absorption question, see Seeley D. and Berendzen R. , “The development of research in interstellar absorption, c. 1900–1930”, Journal for the history of astronomy, iii (1972), 52–64, 75–86, espec. pp. 75–79.

Comstock G. C. , “Provisional results of an examination of the proper motions of certain faint stars”, Astronomical journal, xxiv (1904), 43–49; and Kapteyn J. C. , “Remarks on the determination of the number and mean parallax of stars of different magnitude and the absorption of light in space”, Astronomical journal, xxiv (1904), 115–23.

Kapteyn to Babcock Harold D. , 8 November 1909 (KAL Archives).

Kapteyn J. C. , “On the absorption of light in space”, Astrophysical journal, xxx (1909), 284–317.

Hale to Kapteyn , 6 January 1914 (Hale Microfilm). At first the tentative results of Adams and Seares were not published, but communicated by Hale to Kapteyn (who was living in Holland) so that the latter could examine the material and offer his opinion of the results; Kapteyn to Hale , 11 September 1913, and Hale to Kapteyn , 6 January 1914 (Hale Microfilm).

Kapteyn to Hale , 12 February 1914 (Hale Microfilm).

Hale to Kapteyn , 29 May 1914 (Hale Microfilm). On the recognition of selective absorption as significant, see also Kapteyn to Hale , 6 April 1914, and Hale to Kapteyn , 11 May 1914 (Hale Microfilm).

Kapteyn to Hale , 29 March 1914 (Hale Microfilm).

Shapley to Hale , 14 November 1912; Hale to Shapley , 26 December 1912 (Hale Microfilm).

Shapley to Moulton F. , 7 January 1916 (Shapley Archives). For a review of Shapley's cluster colour studies work, see his “Studies based on the colors and magnitudes in stellar clusters. First part: The general problem of clusters; Second part: Thirteen hundred stars in the Hercules cluster (Messier 13)”, Astrophysical journal, xl (1917), 118–40.

Kapteyn to Shapley H. , 17 August 1915 (Shapley Archives). For similar remarks about Shapley's innovative work, also see Kapteyn to Hale , 7 March 1915 (Hale Microfilm).

Kapteyn to Hale , 23 September 1915 (Hale Microfilm).

Kapteyn to Hale , 18 February 1908 (Hale Microfilm). Kapteyn J. C. , “On the number of stars of determined magnitude and determined galactic latitudes”, Groningen publications, xviii (1908); and idem, “On the mean star-density at different distances from the solar system”, Koninklijke Akademie van Wetenschappen te Amsterdam. Proceedings of the section of sciences, x (1908), 626–35.

See Kapteyn , “On the luminosity of the fixed stars” (ref. 36), 670–4, espec. p. 670.

Kapteyn to Hale , 21 September 1909 (Hale Microfilm).

Kapteyn to Adams , 11 November 1912 (Hale Microfilm).

Kapteyn to Hale , 26 March 1916 (Hale Microfilm).

Seeliger H.V. , “Die Vertheilung der Sterne auf der nordlichen Halbkugel nach der Bonner Durchmusterung”, Sitzungsberichte der Mathematisch-Physikalischen Klasse der K. Bayerischen Akademie der Wissenschaften zu München, xiv (1884), 521–48; and idem, “Über die Vertheilung der Sterne auf der sudlichen Halbkugel nach Schoenfeld's Durchmusterung”, ibid., xvi (1886), 220–51.

Nort H. , “The Harvard map of the sky and the Milky Way”, Recherches astronomiques, vii (1917), 1–117.

Kapteyn J. C. and van Rhijn P. , “On the distribution of the stars in space especially in the high galactic latitudes”, Contributions of the Mount Wilson Observatory, no. 188 (1920), reprinted in Astrophysical journal, lii (1920), 23–38, p. 29.

Kapteyn J. C. and Pickering E. C. , “Durchmusterung of selected areas between δ = 0 and δ = + 90°, Systematic plan”, Annals of the Harvard College Observatory, ci (1918).

Kapteyn to Hale , 17 March 1918 (Hale Microfilm).

Hale to Kapteyn , 3 December 1912. Also see Kapteyn's response to Hale, 31 December 1912 (Hale Microfilm), in which Kapteyn generally concurs with Hale. For Gill's concern, see Gill to Kapteyn , 27 March 1907, and Gill to Pickering , 25 October 1912 (KAL Archives), in which Gill chides Pickering for soliciting Kapteyn's assistance. In correspondence with Hale as early as 1905, Kapteyn expressed his devotion to the theoretical side of these questions, but lamented the fact of the paucity of relevant data; see Kapteyn to Hale , 7 May 1905 (Hale Microfilm).

Kapteyn and Van Rhijn , “On the distribution of the stars in space especially in the high galactic latitudes” (ref. 57), 23–24.

See Schwarzschild K. , “Über die Integralgleichungen der Stellarstatistik”, Astronomische Nachrichten, clxxxv (1910), cols 81–88, espec. cols 85–86.

Kapteyn and Van Rhijn , “On the distribution of the stars in space especially in the high galactic latitudes” (ref. 57), 34–35.

Trumpler R. J. and Weaver H. F. , Statistical astronomy (Berkeley, Calif., 1953), 438. Also see Hale G. E. , “Professor Kapteyn's investigations”, Mount Wilson Observatory reports, no. 19 (1920), 254–5.

Kapteyn to Shapley , 15 June 1919 (Shapley Archives). Shapley's assertion of an eccentric Sun was based on the assumption that globular clusters are centrally distributed about the Galaxy.

Shapley to Kapteyn , 7 March 1920 (Shapley Archives).

For a complete analysis of the Dutch reaction to Shapley's cosmology (spearheaded by Kapteyn and van Rhijn), see my paper “The death of a research programme: Kapteyn and the Dutch astronomical community”, Journal for the history of astronomy, xii (1981), 77–94.

Kapteyn J. C. , “First attempt at a theory of the arrangement and motion of the sidereal systems”, Astrophysical journal, lv (1922), 302–28. Kapteyn had been working on the gravitational distribution of forces since at least early 1921; see Kapteyn to Hale , 4 April 1921, 30 July 1921, and 3 January 1922 (Hale Microfilm).

The results of Kapteyn's latter work had been communicated at the Edinburgh meetings of the BAAS in September 1921. Since Jeans was present, it was known to him prior to publication. Working independently, though relying on much the same data, he reached basically the same conclusions as Kapteyn. See Jeans to Kapteyn , 28 December 1921 (University of Groningen Archives), and Jeans J. H. , “The motions of the stars in a Kapteyn-Universe”, MNRAS, lxxxii (1922), 122–32. For a discussion of Jeans's support of the “Kapteyn Universe”, within his force studies, and implications for the “island universe” theory, see Smith , Expanding universe (ref. 1), 104–5.

Kapteyn and Van Rhijn , “On the distribution of the stars in space especially in the high galactic latitudes” (ref. 57), 33.

Hale to Kapteyn , 18 February 1913 (Hale Microfilm).