Stellar Temperature Scales

relations between quantities obtained from observations characterizing the energy distribution in the spectrum of a star (spectral class, color index, and others) and the effective temperature. These relations are used when comparing the results of theoretical studies of stellar structure and evolution with observations.

In order to determine stellar temperature scales, it is necessary to know the linear dimensions of the star and the total quantity of energy radiated by it. These circumstances introduce difficulties in determining stellar temperature scales associated with the necessity of photometry of stars in the far ultraviolet and infrared regions of the spectrum and with the small number of stars of known radii (principally the closest stars—supergiants and eclipsing variable stars). In the same spectral class the dwarfs are hotter than the giants and supergiants, since, because of the lesser force of gravity on the surface of the last two, the same degree of ionization and excitation of the atoms, which determines the spectral class, is attained at a lesser temperature. Table 1 gives a stellar

temperature scale compiled on the basis of the data of the American astronomers H. Johnson (1966) and D. Morton and T. Adams (1968), which has been confirmed by the latest measurements.