How do masses differ as we look along the main sequence on an H-R diagram?
” Along the main sequence of the H-R diagram the blue stars in the upper left area have more mass than the red stars in lower right. The greater the mass of the star, the greater its surface temperature and the greater its luminosity. Mass is the important factor in luminosity because the more the outer layers weigh, the more nuclear burning takes place in a star’s core to maintain gravitational equilibrium. “What do we mean by a star’s main sequence lifetime? Explain why more massive stars lead shorter lives.” A star’s main sequence lifetime is the time when it still has hydrogen in its core to fuse into helium. The more massive stars have shorter main sequence lifetimes because their great mass and luminosity leads to faster hydrogen consumption. “What are the Cepheid variables? What is the period-luminosity relation for Cepheids, and why is it useful for distance measurements?” The Cepheid variables are a special category of very luminous pulsating variable stars. A variable star is
