Edwin Hubble (1889-1953) joined the Mount Wilson Observatory staff in 1919, a few years after earning his Ph.D. from the University of Chicago. His research goal was to study galactic nebulae (the nebulous objects scattered throughout the Milky Way). He would perform that research on the newly completed 100-inch Hooker telescope, the largest in the world at that time.
T. A. Rector/B. A. Wolpa/NOAO/AURA/NSF