Edwin Hubble

Edwin Powell Hubble (November 20, 1889 – September 28, 1953)^[1] was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology.^[2][3]

Hubble proved that many objects previously thought to be clouds of dust and gas and classified as "nebulae" were actually galaxies beyond the Milky Way.^[4] He used the strong direct relationship between a classical Cepheid variable's luminosity and pulsation period^[5][6] (discovered in 1908 by Henrietta Swan Leavitt^[7]) for scaling galactic and extragalactic distances.^[8][9]

Hubble confirmed in 1929 that the recessional velocity of a galaxy increases with its distance from Earth, a behavior that became known as Hubble's law, although it had been proposed two years earlier by Georges Lemaître.^[10] The Hubble law implies that the universe is expanding.^[11] A decade before, the American astronomer Vesto Slipher had provided the first evidence that the light from many of these nebulae was strongly red-shifted, indicative of high recession velocities.^[12][13]

Hubble's name is most widely recognized for the Hubble Space Telescope, which was named in his honor, with a model prominently displayed in his hometown of Marshfield, Missouri.