Edward C. Pickering

Draper Memorial Photographs of Stellar Spectra Exhibiting Bright Lines

THE spectra of ordinary stars, whether examined directly by the eye, or indirectly by means of photography, present little variety. The comparatively few cases of deviation from the usual type are therefore particularly interesting, and the occurrence of bright lines in a stellar spectrum constitutes perhaps the most singular exception to the general rule. The brightness of the F line in the spectra of γ Cassiopeiæ and β Lyræ was noticed by Secchi. Rayet afterwards found three rather faint stars in Cygnus, the light of which was largely concentrated in bright lines or bands. The adoption at the Harvard College Observatory of a system of sweeping, with a direct-vision prism attached to the eye-piece of the equatorial telescope, resulted in the discovery by the present writer of several additional objects of the same class. Still more recently, Dr. Copeland, during a journey to the Andes, has extended the list by the dis covery of some similar stars in the southern heavens.