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The Density of Molecules in Interstellar Space

Nature volume 95, pages 701–703 (1915)Cite this article

Abstract

IN recent years evidence has been brought forward by several investigators1 indicating that light from distant stars suffers a slight attenuation in travelling through interstellar space. In particular a recent investigation by Jones2 assigns fairly definite numerical values to coefficients of attenuation corresponding to “photographic” and “visual” light from stars of known proper motions and spectral types the magnitudes of which had been carefully measured by Parkhurst3 for light of these wave-lengths. If, as seems reasonable, this extinction is assumed to be due to attenuation by scattering in travelling through a “residual” gas occupying, interstellar space, we are enabled to estimate the average density of molecules in the intervening regions, following a method due originally to Larmor4 for assigning an upper limit to the density of matter in comets' tails.

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References

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  9. Jones' determination is in fair agreement with Kapteyn's final result, (Astrophysical Journal, vol. xxx, p. 398): [(photographic)-(visual)] losses = +0m0031 â 0.0006. The corresponding determinations by King (E. S.) of the coefficients of attenuation for photographic and visual light give values about five times that of the text.

  10. The losses + 0m0080 and +0mc033 estimated by Jones forPhoto-graphicandvisuallight lead to the values K1δ = 0.0073 and K2δ = 0.0030 (wive-lengths not stated). Kapteyn's (corrected) estimate for wavelength λ1 = 0.431ⵠis Kjδ = 0.00507, leading to the value n = 0.068 - 105 hydrogen molecules per cm.3, which is of the same order of magnitude as the determination already made. E. S. King's results (footnote 1) increase the estimate of the text about five-fold.

  11. Note a discussion on this point by H. C. Plummer in a paper by H. H. Turner, loc. cit. (footnote 1).

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  21. On this point note a remark by Eddinton, loc. cit., p. 258.

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  1. McGill University, Montreal

    LOUIS VESSOT KING

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  1. LOUIS VESSOT KING
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KING, L. The Density of Molecules in Interstellar Space. Nature 95, 701–703 (1915). https://doi.org/10.1038/095701b0

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