Walter Baade

the long version

"Although less well known outside the field than Edwin Hubble, Walter Baade was arguably the most influential observational astronomer of the twentieth century. Written by a fellow astronomer deeply familiar with Baade and his work, this is the first biography of this major figure in American astronomy. In it, Donald Osterbrock suggests that Baade's greatest contribution to astrophysics was not, as is often contended, his revision of Hubble's distance and age scales for the universe. Rather, it was his discovery of two distinct stellar populations: old and young stars. This discovery opened wide the previously marginal fields of stellar and galactic evolution - research areas that would be among the most fertile and exciting in all of astrophysics for decades to come."--BOOK JACKET.