Bengt G.D. Strömgren
From Sonoma State University:
Strömgren did important research in stellar structure in the 1930s, but he is best known for his theory of the ionized gas clouds around hot stars. He found relations between the gas density, the luminosity of the star, and the size of the “Strömgren sphere” of ionized hydrogen around it. He surveyed such H II regions in the Galaxy, and he also did important work on stellar atmospheres and ionization in stars. He calculated the relative abundances of the elements in the sun and other stars and worked on optical design and, for many years, on the development of photoelectric photometry.