B.P. Schmidt, R.P. Kirshner, "Expanding photospheres of Type II supernovae and the extragalactic distance scale," Astrophysical Journal, 395:366-86, 1992.

Brian P. Schmidt (Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.): "Determining the value of the Hubble Constant, Ho, has been an area of considerable interest since Edwin Hubble first realized that the universe was expanding in the late 1920s. Ho is the constant of proportionality between the recession velocities of galaxies and their distances. It gives the current rate of expansion of the universe, and is inversely proportional to the age of the universe. Measuring Ho is difficult because there are no direct geometric measures of distance that can be applied to objects beyond our own galaxy. Because the universe does not expand smoothly on scales corresponding to the distances to the nearest galaxies, it is necessary to measure accurate distances to galaxies far beyond the local group to ascertain the...

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