born in Strasbourg (now in France). In 1941 he classified supernovae into Types I and II according to their spectra. In 1954 he and W. Baade reported the first optical counterpart to an extragalactic radio source, Cygnus A. Minkowski went on to specialize in the optical identification of radio sources with high redshift. He also carried out a search for planetary nebulae, doubling the number known.