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Nature volume 50, pages 254255 | Download Citation



THE STECTRUM OF THE ORION NEBULA.—Two papers on the spectrum of the nebula in Orion are contained in the current number of Astronomy and Astro-Physics, one by Prof. J. E. Keeler, and the other by Prof. W. W. Campbell. The former observer photographed the spectrum of the nebula many times during last winter. A comparison, of the photographic and visual observations of nebular lines, with dark lines in the spectra of the Orion stars, indicates that an intimate relation exists between the two. “Indeed,” says Prof. Keeler, “taking into account the relative intensities of the lines, the spectrum of Rigel mayalmost be regarded as the nebular spectrum reversed.” Spectroscopists will remember that Dr. Huggins obtained an anomalous spectrum of the Orion nebula in 1889, his photograph showing a large number of fine lines apparently connected with the spectra of the trapezium stars, while the hydrogen lines Hδ and Hɛ were absent. Prof. Keeler has tried to obtain the same result by photographing the spectrum in the same way as Dr. Huggins, but without success. He shows that “contrary to the belief which has been held up to the present time, the trapezium stars have spectra marked by strong absorption bands; they have not the direct connection with the nebula that would be indicated by a bright-line spectrum, but are in fact on precisely the same footing (spectroscopically) as other stars in the constellation of Orion. While their relation to the nebula is more certain than ever, they can no longer be regarded as necessarily situated in the nebula, but within indefinite limits they may be placed anywhere in the line of sight. “Finally with regard to the appearances that have led to the belief that the nebular lines are bright in these stars, Prof. Keeler believes that they are of physiological and photographic origin, and do not actually exist. It is pointed out that these conclusions have an important bearing on theories of stellar development

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