The Spectra of the White Dwarfs

Abstract

The discovery that stars of low luminosity existed, with masses near that of the sun and radii near that of the earth, was one of the major surprises of astrophysics [1]. After an early period of observation, an extremely successful and complete theory of their structure was developed [2]. These stars are faint both intrinsically and by apparent magnitude, and detailed investigation of their spectra, colors, parallaxes and masses have been few and difficult. The highly efficient spectrographic equipment of the 200-inch Hale reflector on Palomar Mountain has made possible, for the first time, detailed spectroscopic studies of a large number of these objects; in fact, the majority of suspected or known northern white dwarfs can now be observed. In addition, the growth of photoelectric techniques has provided accurate colors, and soon will provide correlations between colors, luminosities and spectra. Theoretical development in model stellar atmospheres, in the theory of line broadening, and more data on parallaxes are badly needed. Nevertheless we now approach a period in which interpretation of white-dwarf spectra in terms of composition will become profitable.