Criteria and Applications for Spectral Classification Outside the MK Domain

Abstract

The area under discussion here lies beyond the domain of the MK system and includes studies of natural groups as detected in low dispersion studies; it extends to spectral regions studied now in the far ultraviolet and in the infrared and radio regions; in this paper primary consideration is given to optical spectra from the near infrared to the near ultraviolet. We give a description of “natural groups” and a brief description of new possibilities opened for research in this area through the introduction of thin prisms and the combination of prism and grating (GRISM). Finally a summary of spectral criteria useable outside the MK domain is presented.