William Wilson Morgan
William Wilson Morgan ( born January 3, 1906 in Bethesda, Tennessee; † 21 June 1994) was an American astronomer.
He worked at the Yerkes Observatory. A main area of Morgan was the spectral classification. Together with Philip C. Keenan, he developed the MK system. On the basis of distance estimates of O and B stars, he proved the spiral arms of the Milky Way along with Donald Osterbrock and Stewart Sharpless.