Minkowski, Rudolph Leo (1895–1976)

German-born US astrophysicist, responsible for the compilation of a set of photographs now found in every astronomical library, the National Geographic Society Palomar Observatory Sky Survey. A leading authority on novae and planetary nebulae, he was a pioneer in the science of radio astronomy.

Minkowski was born in Strasbourg (then in Germany, now in France) and studied at Breslau, Silesia (now Wrocław, Poland).

He became professor of physics at Hamburg 1922, but the rise of Nazism in Germany caused him to emigrate to the USA 1935. He worked at the Mount Wilson and Palomar observatories in California until 1959, and at the University of California at Berkeley 1960–65.

Minkowski divided supernovae into two principal types, and more than doubled the number of known planetary nebulae. In collaboration with Walter Baade, who had also been his colleague at Hamburg, Minkowski identified a discrete radio source, Cygnus A, in 1951. This was the first time an extragalactic radio source was optically identified.

Minkowski determined the optical red shift of the radio source 3C 295, which was then the farthest point on the velocity–distance diagram of cosmology, in his last observing run at the Palomar 500-cm/200-in telescope.