I compared neither the density of the lines nor their widths, butĪ physiological blend of both effects, which I would call "prominence". The H lineĬould not be used for this purpose as it coincides with H_epsilon. H_delta and H_zeta using a decimal method ,Īs used for brightness estimates of variable stars. Of the continuous evolution of the spectral type is comparison of the calcium ToĪchieve this, I relied on the fact that the most sensitive measure The most accurate determination of the spectral type of stars in the Pleiades. I used the Zeiss UV-prism camera with a prism of lowĭispersion (1.9 mm from H_gamma to H_zeta). Schwarzschild, I have made some long spectral exposures On the Relation Between Brightness and Spectral Type in the Pleiades To make it more accessible for anyone interested in history of stellar astrophysics. Kucera for providing me with a photocopy during his stay at the University of Konstanz), and considering the fact thatĮven here the Rosenberg article is noted only in a footnote (#46), I decided Given my own troubles finding this journal (I am indebted to Jaromir I learned about this unique material fromĪn authoritative account on the history of the HR diagram published by Axel V. June 1910, but note that both Schwarzschild (who proposed the measurements)Īnd Hertzsprung left the observatory already in 1909. In the meantime, Hans Rosenberg (1879≡940) of Göttingen publishedĪ most interesting article in Astronomische Nachrichten. Potsdam 22, 1, 1911) together with a color-magnitudeĭiagram for another winter cluster, the Hyades. Until 1911, when the satisfactory version of the diagram was presented (Publ.Īstrophys. Relation between luminosities and colors of stars suffered from a systematicĮrror due to influence of the secondary spectrum of the objective. However, this first Hertzsprung attempt to visualize the These spectra then directly translated into the effective wavelength The separation of the most intense parts of Image on the photographic plate was accompanied by a very short first-order Nowadays replaced by spectral type or color index, Hertzsprung attachedĪ coarse diffraction grating before the objective so that an ordinary stellar He brought with him a working version with photographic magnitudes Training in photochemistry) visited Karl Schwarzschild at Göttingen, Was constructed by Ejnar Hertzsprung for the stars of the Pleiades.Īlready in 1908, when Hertzsprung (then still an amateur astronomer with Until quite recently, I though that the first published HR diagram
The Göttingen Observatory photo, courtesy Hartmut Grosser. Hearnshaw's excellent history of stellar spectroscopy, The Analysis of Starlight, page 211. A nearly identical picture, taken obviously at the same occasion, is reproduced in John B. Karl Schwarzschild (left) and Ejnar Hertzsprung in front of the Göttingen Observatory building sometime in 1909.
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