One of the preeminent scholars of his time, Edwin Hubble – a man who started earning a law degree on a Rhodes scholarship and then earned a doctorate in astronomy simply because he was tired of of his former profession – went to one of the most powerful telescopes in existence at the time, at Mt. Wilson Observatory in California, to study the skies. Hubble focused his attention on solving the question of nebulae – cosmic dust clouds – with the 100-inch Hooker telescope allowing him to make out individual stars. What he discovered revolutionized the field of astronomy.

On this day, December 30, in 1924 Edwin Hubble announced his findings: the nebulae turned out to be a separate galaxy altogether.

Hubble also discovered Cepheid variable stars, which brighten and dim on a regular basis, and using which a bright Harvard scholar Henrietta Leavitt figured calculated distances. It turned out the Cepheid stars were much further away than previously thought, beyond the bounds of the Milky Way. Hubble’s advances led to finding many more galaxies and the calculations they were moving away from ours – that the universe was still expanding.