Edwin Powell Hubble ( November 20 , 1889 â `` September 28 , 1953 ) was an American astronomer who helped our understanding of the universe by showing us that there are galaxies other than our own , the Milky Way . Edwin Powell Hubble ( November 20 , 1889 â `` September 28 , 1953 ) was an American astronomer who profoundly changed understanding of the universe by confirming the existence of galaxies other than our own , the Milky Way .