Abstract
MATTEE IN INTERSTELLAR SPACE.—The existence of interstellar calcium, as evidenced by the detached [H] and [K] lines in stellar spectra, has for some time engaged the attention of Dr. O. Struve (see, for example, NATURE, vol. 122, p. 252). His latest researches, made in collaboration with Prof. B. P. Gerasimovič, and described in the Astrophysical Journal, vol. 69, p. 7, deal with the physical properties of calcium and other elements in interstellar regions. Eddington's hypothesis of an interstellar substratum embodying the whole galactic system is regarded as the most satisfactory hypothesis at present, and the one most in accordance with both observational data and theoretical considerations. This substratum consists of many elements in various states of ionisation, with an average density of the order of 10-26. The observed intensities of detached Ca+ lines show a definite distance effect, such as would be expected from a uniform distribution of Ca+ with a density of about 3.6 × 10-32. The substratum of interstellar matter appears to share the rotational motion of the stars round a distant central mass in galactic longitude 325°.
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Our Astronomical Column. Nature 123, 886 (1929). https://doi.org/10.1038/123886a0
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DOI: https://doi.org/10.1038/123886a0