Accuracy of Spectral Classification

Extract

A knowledge of the spectral types of visual components is still basic to most intensive studies of visual systems. Although there are photoelectric techniques that give good quantitative information on certain classes of stars, the only way at present to identify most classes of stars, from mercury-manganese stars to barium stars, is by obtaining their spectra. The spectra can be obtained from objective prisms, slit spectrographs, or spectrum scans, but the important things are that they (1) show a large portion of the spectra, preferrably in the blue-violet for most classes of stars, (2) have sufficient resolution and signal-to-noise to identify many spectral lines, and (3) be standardized as an independent system. The last is important because if spectral type standards are changed so that they will agree with other information, such as colors, we lose the benefits of a comparison, such as deriving interstellar reddening.