Quantitative Spectral Classification of Solar - Stars and the Sun.

Spectroscopic observations of solar-type stars at a dispersion of 40 A/mm are used to derive quantitative indices which are strongly correlated with B-V photoelectric color and absolute magnitude. For stars which have no peculiarities in their spectra, B-V and Mv indices are determined and used to place a star in the color-magnitude diagram, and the calibration of the diagram in terms of MK spectral type is used to derive the spectral type of the star. Application of MK spectral classification standards in the G0-G5 region indicates that the revised list of Morgan and Keenan is a more self-consistent set of standards than is the list of Johnson and Morgan. Examination of the lunar reflection of the solar spectrum indicates a spectral type of G4V. This result is typical of quantitative spectroscopic classifications of the sun while photoelectric measures of the solar flux are consistent with a solar spectral type of G2V.