Stellar evolution and the population concept after 1950; The Vatican conference (Q1574480)

The author presents the development of the concept of stellar populations after 1950. He exposes the scheme of Walter Baade (1944) on stellar populations and presents the works of the Vatican conference on the problem of stellar populations (1957). There are discussed the contributions of O'Connell, Eggen-Johnson, Sandage, Walker, Chandrasekharan-Schönberg, Hoyle, Ooort and Schwarzschild. Special sections are devoted to the presentation of disk population and to the new picture of galactic evolution and later developments.