The Development of Research in Interstellar Absorption,c. 1900–1930: Part 2

Comstock George C. , “Provisional Results of an Examination of the Proper Motions of Certain Faint Stars”, Astronomical journal, xxiv (1904), 46–9.

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, xiv (1904), 115–22.

Even Kapteyn's form for ψ (L) was too simple to correspond to reality, but it was a better approximation than Comstock had adopted. Kapteyn's luminosity function in terms of absolute magnitudes was expressed by where M_σ and σ were constants chosen to fit the data.

Op. cit. (ref. 33), 2.

Ibid., 3.

Kapteyn J. C. , “On the Absorption of Light in Space”, Astrophysical journal, xxx (1909), 284–317.

Kapteyn originally reported a value for absorption of about 0^m·5/kpc. He discovered an error in his average distances of a factor of 1·7 which he reported to G. E. Hale (see letter, J. C. Kapteyn to G. E. Hale, 7 November 1909, in the Hale microfilm collection, Pasadena). The absorption he originally reported had to be divided by this factor for his results to be valid.

Letter, J. C. Kapteyn to G. E. Hale, 14 January 1913, in Hale microfilm collection, Pasadena.

Letter, G. E. Hale to J. C. Kapteyn, 6 January 1914, in Hale microfilm collection, Pasadena.

Among the investigations that Kapteyn reviewed were: Fath E. A. , “The Integrated Spectrum of the Milky Way”, Astrophysical journal, xxxvi (1912), 362–7; King E. S. , “Photographic Magnitudes of 153 Stars”, Annals of Harvard College Observatory, lix (1912), 157–86; Turner H. H. , “Interstellar Space”, Monthly notices of the Royal Astronomical Society, lxix (1909), 61–71; Pickering E. C. , Harvard circular, no. 170; Seares F. H. , Mt Wilson contributions, no. 81 (1913); Adams W. S. , “Note on the Relative Intensity at Different Wavelengths of the Spectra of Some Stars Having Large and Small Proper Motions”, Astrophysical journal, xxxix (1914), 89–92; and several unpublished works by Barnard, Hertzsprung, and van Rhijn.

Kapteyn J. C. , “On the Change of Spectra and Color Index with Distance and Absolute Brightness. Present State of the Question”, Astrophysical journal, xl (1914), 187.

Russell Norris Henry and Shapley Harlow , “On the Distribution of Eclipsing Variable Stars in Space”, Astrophysical journal, xl (1914), 417–34.

See Shapley Harlow , “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, xlv (1917), 118–40.

Of course, if space were transparent, the paradox of Olbers would once more be a paradox, Shapley noted. A solution to the problem, proposed by Shapley (ibid., 139), was to reconsider our view of an infinite universe. By universe … we mean the system that is formed by stars of the kind that surround the sun and appear to us in all parts of the sky. Either the extent of the star-populated space is finite, or “the heavens would be a blazing glory of light”, or there is an absorption of light in space…. Then, since the heavens are not a blazing glory, and since space absorption is of little moment throughout the distances concerned in our galactic system, it follows that the defined stellar system is finite.

Letter, Kapteyn J. C. to Hale G. E. , 23 September 1915, Hale microfilm collection, Pasadena.

Private communication, 23 December 1969.

Op. cit. (ref. 50), 281.

Private communication with Nicholas Mayall, 13 April 1970.

Shapley Harlow , “Studies of the Galactic Center. IV. On the Transparency of the Galactic Star Clouds”, Proceedings of the National Academy of Sciences, xv (1929), 174–7.

Shapley Harlow , “Relation of Apparent Magnitude to Angular Diameter of Globular Clusters”, Harvard bulletin, no. 864 (1929), 7–9.

Trumpler Robert , “Preliminary Results on the Distances, Dimensions and Space Distribution of Open Star Clusters”, Lick Observatory Bulletin, xiv (1930), 154–88.

Letter, Trumpler R. to Aitken R. , 28 January 1930, at Lick Observatory.

“Reports of the Observatories, 1929–1930”, Publications of the American Astronomical Society, vi (1931), 395–6.

Op. cit. (ref. 77), 163.

Ibid., 166–7.

Ibid., 185.

Bottlinger K. F. and Schneller H. , “Uber die Interstellaire Absorption innerhalf Milchstrasse”, Zeitschrift fur Astrophysik, i (1930), 339–42.