Why would an eclipsing binary be more valuable than an ordinary spectroscopic binary in accurately determining stellar parameters? (hint: consider the spectroscopic information here.) describe three differences in the p-p chain and cno cycle for converting h into he in main sequence stars. explain why type ia supernovae are favoured for determining distances to galaxies, how they could be distinguished from type ii supernovae, and explain at least one drawback in their use as standard candles. list three observations that suggest that much of the matter in the universe is "dark." explain differential rotation of the galaxy and how it affects observations of the spectra of stars in the galaxy relative to an observer on earth. why can’t an isolated white dwarf contract as it cools? what is its fate?