1.) the difference in the brightness of two stars with the same surface temperature is attributable to their colors densities ages sizes 2.) most responsible for the formation of a star is force. electromagnetic gravitational interstellar nuclear 3.)which main-sequence stars are the most massive? yellow orange red blue 4.) a spinning neutron star that appears to give off radio wave pulses is called a supernova white dwarf pulsar black hole 5.) greater redshifts in the spectra of galaxies indicate faster speeds lower temperatures slower speeds higher temperatures