Abstract
THE SPECTRUM OF β LYRÆ.—A study of twenty-nine photographs of the spectrum of β Lyræ has led to some interesting results, noted by Prof. E. C. Pickering in Astronomische Nachrichten, No. 3051. The spectrum of this star contains, in addition to the absorption lines, several bright lines, the most conspicuous of which are about λλ 486, 443, 434, 410, 403, and 389, to use a three-figure reference. The lines near λ 443 and λ 403, are two of the most prominent lines in the spectra of the Orion stars, and the remaining four coincide with the hydrogen lines F, G, h, and α. From the investigation it appears that these bright lines change their positions, so that sometimes they have a greater wave-length than the corresponding dark lines, whilst at other times the reverse is the case. In some of the photographs several bright lines are double, and the dark lines are also not free from changes. This naturally led to the in quiry as to whether the changes were connected with the variations of the star's brightness. Starting from a minimum of brightness there is a maximum at 3d. 5h., a secondary minimum at 6d. 11h., another maximum at 9d. 16h., and then the principal minimum is again reached after a total period of 12d. 22h. The point of interest is that the fourteen plates in which the wave-length of the bright lines was increased were taken during the first half of this period of variation—that is, before the secondary minimum; whilst on the eleven plates taken during the second half of the period the displacement was towards the blue end of the spectrum. And since the photngraphs extend over more than four years, there can be little doubt that the displacements are intimately connected with the variations of the star's brightness. One of the explanations suggested by Prof. Pickering to account for the observed phenomena is that the bright lines are emitted by an object revolving in a circular orbit round the principal star, with a maximum velocity of about 300 miles per second, and completing its circuit in a period of 12d. 22h. The corresponding periastron distance is about 50,000,000 miles. If this be so, β Lyræ is a binary of the β Aurigæ type, but differing from it in the fact that the component stars have unlike spectra. The phenomena could also be produced by a meteor stream, or by an object like the sun, rotating in 12d. 22h., and having a large protuberance on it extending over more than 180° of longitude. The study of the additional photographs which are being taken will doubtless elucidate the matter.
Article PDF
Rights and permissions
About this article
Cite this article
Our Astronomical Column. Nature 44, 355 (1891). https://doi.org/10.1038/044355a0
Published:
Issue Date:
DOI: https://doi.org/10.1038/044355a0