Walter Baade
Minkowski was the son of Marie Johanna Siegel and physiologist Oskar Minkowski. His uncle was Hermann Minkowski, a mathematician and one of Einstein's teachers in Zürich. Rudolph studied supernovae and, together with Walter Baade, divided them into two classes (Type I and Type II) based on their spectral characteristics. He and Baade also found optical counterparts to various radio sources.