Walter Baade was born on March 24, 1893, in Schröttinghausen, Westphalia, Germany. While still in high school, he began to cultivate his interest and talents in astronomy. He obtained a Ph.D. at Göttingen in 1919 and spent eleven years on the staff of the University of Hamburg. He moved to the United States in 1931 and started working at the Mt. Palomar and Mt. Wilson observatories, where he remained until returning to Germany in 1958. In 1958, he was also awarded the American Astronomical Society's Henry Norris Russell lectureship, honoring a lifetime of distinguished achievement in astronomy. He died on June 25, 1960.

In the 1930s, Baade and his colleague Fritz Zwicky were among the first to suggest that neutron star s were the remnant cores of massive stars that had ended their lives as supernoae. But Baade made his greatest contributions to astronomy during World War II. Because Los Angeles...