[4][5] His uncle was Hermann Minkowski, a mathematician and one of Einstein's teachers in Zürich.
[6] He and Baade also found optical counterparts to various radio sources.
He headed the National Geographic Society – Palomar Observatory Sky Survey, a photographic atlas of the entire northern sky (and south to declination -22°) down to an apparent magnitude of 22.
[2] Together with Albert George Wilson, he co-discovered the near-Earth Apollo asteroid 1620 Geographos in 1951,[7] and he also discovered Planetary Nebula M2-9.
He additionally discovered a correlation between the luminosity of early-type galaxies and their velocity dispersion,[8] which was later quantified by Faber and Jackson.