Anchor Points for the MK System of Spectral Classification

The Atlas of Stellar Spectra was published fifty years ago by W.W. Morgan, P.C. Keenan, and E. Kellman (1943). Since then, there have been supplementary lists of standard stars and atlases published by Morgan and/or Keenan in 1953, 1973, 1976, and 1978. In these later publications, some of the types for the standard stars were modified in the light of better data. However, certain stars have remained as anchor points of the MK System and have not been refined or changed in any way. New spectra of these stars have been inter-compared to confirm their consistency. A table of these most fundamental anchor points has been compiled and is presented here for comment.