November 20: Edwin Powell Hubble

Edwin Powell Hubble

November 20, 1889 – September 28, 1953

Edwin Hubble was an American astronomer. He profoundly changed our understanding of the universe by demonstrating the existence of other galaxies besides the Milky Way. He also discovered that the degree of redshift observed in light coming from a galaxy increased in proportion to the distance of that galaxy from the Milky Way. This became known as Hubble's law, and would help establish that the known universe is expanding.

In 1919, Hubble was offered a staff position in California by George Ellery Hale, the founder and director of the Carnegie Institution's Mount Wilson Observatory, near Pasadena, California, where he remained on the staff until his death. Shortly before his death, Mount Palomar's giant 200-inch (5.1 m) reflector Hale Telescope was completed, and Hubble was the first astronomer to use it. Hubble continued his research at the Mount Wilson and Mount Palomar Observatories, where he remained active until his death.

Edwin Hubble's arrival at Mount Wilson, California, in 1919 coincided roughly with the completion of the 100-inch (2.5 m) Hooker Telescope, then the world's largest telescope. At that time, the prevailing view of the cosmos was that the universe consisted entirely of the Milky Way Galaxy. Using the Hooker Telescope at Mt. Wilson, Hubble identified Cepheid variables (a kind of star; see also standard candle) in several spiral nebulae, including the Andromeda Nebula. His observations, made in 1922–1923, proved conclusively that these nebulae were much too distant to be part of the Milky Way and were, in fact, entire galaxies outside our own. This idea had been opposed by many in the astronomy establishment of the time, in particular by the Harvard University-based Harlow Shapley. Hubble's discovery, announced on January 1, 1925, fundamentally changed the view of the universe.

Hubble also devised the most commonly used system for classifying galaxies, grouping them according to their appearance in photographic images. He arranged the different groups of galaxies in what became known as the Hubble sequence.

Hubble was awarder the Bruce Medal (1938) and the Gold Medal of the Royal Astronomical Society (1940).

The Lunar crater Hubble, asteroid 2069 Hubble and the orbiting Hubble Space Telescope are named in his honor.