Edwin Hubble

(1889 - 1953 AD)

American astronomer who determined the extragalactic distance scale by locating Cepheid variables in the galaxy M31 from the Mount Wilson Observatory in 1924 and NGC 6822 in 1925. Using the galactic period-luminosity relationship (which was actually not quite correct, as was discovered by Baade), he determined distances. Extending distance determinations by using the brightest star in galaxies, he (with Humason) proposed the Hubble law, which states v = Hl. Hubble's original 1936 value for H of 526 km s^-1 Mpc^-1 was reduced to 200 km s^-1 Mpc^-1 after the work of Baade, and to between 50 and 100 km s^-1 Mpc^-1 when Sandage discovered that some of the "stars" Hubble had identified in distance galaxies were actually H II regions. Hubble gives an account of the discovery of the extragalactic nebulae (galaxies) in Realm of the Nebula (1936).

**The preceding information is provided by the Eric Weisstein's World of Scientific Biogra.**