Some Observational Aspects of Stellar Evolution

The interplay between theory and observation in astronomy has nowhere been more successful than in the field of stellar evolution. Modern theories of stellar evolution have been, in outline, firmly fixed for more than ten years, and the observations upon which they were based, as well as some derivative observations and suggested alterations in the theories, have been described in detail by Sandage (1) and Burbidge (2). The general ideas so well entrenched that any discrepant result of a fundamental kind must stand the most careful scrutiny. Because the field of stellar evolution is too large to cover completely in a short article, only a few topics of current interest to the writer are discussed.