Milky Way, Andromeda. Different from formation of stars in that galaxies often collide, or even merge. From mass, deduce luminosity By comparing observed brightness and luminosity, distance can be determined. Hubble's constant x distance Hubble's constant H 0 is not very well known. See HST results on observations of Cepheids in distant galaxies.
Radio galaxies emit tremendous amounts of energy at radio wavelength.
Some of them have huge lobes, which appear to be jets of material ejected from the galaxy. The best explanation of the power of active galaxies and and the even more incredibile power of quasars is that they are powered by accretion disks surrounding giant black holes at the centers of galaxies. New results from HST appear to confirm the theory that quasars are associated with the cores of young galaxies. Return to table of contents. This document was last updated September 4, 1998.