Abstract
THE MAGNESIUM SPECTRUM AS A CRITERION OF STELLAR TEMPERATURE.—The variations undergone by the spectrum of magnesium when the element is subjected to different temperatures were studied some years ago, and their use in estimating the comparative temperatures of celestial bodies have been pointed out. Prof. J. E. Keeler contributes a note on the matter to the Astronomische Nachrichten, No. 3245, his remarks referring especially to some observations recently published by Prof. Scheiner on the behaviour, under different temperatures, of the lines at λ 4482 and λ 4352. The former line is strong and broad in the spectrum of magnesium, when luminosity is produced by means of the electric spark with Leyden jar in the circuit, but it does not appear in the arc spectrum; on the other hand, the line at λ 4352 is strong in the arc spectrum, but faint in the spark spectrum. Similar differences of relative intensity are found to exist in stellar spectra, and Prof. Scheiner is not alone in thinking that they afford a means of estimating the approximate temperatures of the absorptive atmospheres of celestial bodies exhibiting them. In connection with this subject, Prof. Keeler comments upon the absence of the magnesium triplet b from the spectrum of Rigel, while the line at λ 4482 is conspicuous. He suggests that the star is at too high a temperature for the production of the b group, and uses the relative strength of the group in different spectra as a criterion of stellar temperature. It is pointed out that Kayser and Runge have shown that the group is characteristic of a molecular structure which cannot exist at a very high temperature, whereas the lines at λ 4482 and λ 4352 do not represent the same molecular state. These considerations lead to the conclusion that the aspect of the b lines in stellar spectra may be used as an index to the temperature in the same way as the two lines selected by Prof. Scheiner. And since the b group is absent from the spectra of Rigel and certain other stars, it is thought that these bodies must be at a temperature higher than that of the most powerful electric spark, for, were they at this temperature, laboratory observations indicate that the group should be well visible in their spectra.
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Our Astronomical Column. Nature 50, 364–365 (1894). https://doi.org/10.1038/050364a0
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DOI: https://doi.org/10.1038/050364a0