Walter Baade

Walter Baade was a German-American astronomer who made significant contributions to our understanding of stars and galaxies. He is best known for identifying two distinct types of stars in the Milky Way, known as Population I and Population II stars, which differ in age, composition, and location. His work also helped establish the concept of the expanding universe and contributed to measuring distances in space, which are crucial for understanding the scale of the cosmos. Baade's insights have been fundamental in shaping modern astrophysics and our knowledge of how stars evolve.