Abstract
THE DARK-LINE SPECTRUM OF NOVA AQUILÆ.—Dr. J. Lunt has sent to NATURE some interesting details relating to the transient dark-line spectrum of Nova Aquilas, as photographed at the Cape Observatory with the McClean spectrograph on June 10, 11, and 12. Apart from the bright and dark hydrogen spectrum which was in process of development, the spectrum was a continuous one crossed by a true absorption spectrum consisting principally of the enhanced lines of titanium, iron, chromium, strontium, calcium, magnesium, and helium. As shown by iron comparison spectra, the entire series of lines was displaced to the violet by an amount representing a radial velocity of 1500 km. per second (June 11 and 12). The violet edges of broad absorption lines, left partially uncovered by broad bright bands, do not appear to be in question, and the displacement is regarded as a true Doppler effect, due to the actual motion of a stellar body possessing an intensely heated atmosphere of metallic vapours. As in the case of other novæ, the fine dark H and K lines appeared nearly in their normal positions, but Dr. Lunt thinks it erroneous to consider their small displacements as representing the velocity of the star; it seems to him more probable that these lines do not originate in the nova itself, but in a nebulous mass lying in the line of sight. The residual incandescent and disturbed nebulous matter left behind after the passage of a rapidly moving star into a nebula would seem to offer a sufficient explanation of the bright-line spectrum. To account for the supposed enormous velocity of the nova, Dr. Lunt suggests that our own system may have a velocity comparable with those found for spiral nebulæ, and that the velocity may result, in part from this motion, and in part from the high velocity of a wandering star which has come from outside our system.
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Our Astronomical Column . Nature 102, 194 (1918). https://doi.org/10.1038/102194a0
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DOI: https://doi.org/10.1038/102194a0