Page 2, External Galaxies II: [Previous Page] [Next Page] [Class Home Page] Text Pages 369 - 370

With the exception of the Supernova, and a few other techniques still being developed, the most distant sources in our galaxy are measured based on the expansion of the universe. Hubble was the first to notice that the more distant a galaxy was, the higher its speed away from us was.. (Doppler Shifted Spectrum)


Plotting distance verses its speed, Hubble came up with the Hubble Law. H_o is the Hubble Constant, measured in velocity per distance (km/s per Mega parsec).



This is extremely powerful: Doppler Shifts are easy to measure, so distances are easy to get for galaxies using this technique. However, the VALUE of the Hubble Constant is critical