What is the criterion that signifies when a star鈥檚 main sequence life has ended?

What is the criterion that signifies when a star鈥檚 main sequence life has ended?What is the criterion that signifies when a star鈥檚 main sequence life has ended?A star moves off the main sequence when it has exhausted its supply of hydrogen and begins the nucleosynthesis of heavier elements.What is the criterion that signifies when a star鈥檚 main sequence life has ended?"The continuous fusion of hydrogen into helium will cause a build-up of helium in the core. The rate at which this process occurs depends on the initial mass of the star and ranges from millions to billions of years. Larger, hotter stars produce helium more rapidly than smaller, cooler ones.



The accumulation of helium in the core causes a gradual increase in the rate of fusion and gravitational self-compression, as helium is denser than hydrogen. Higher temperatures must be attained to resist this increase in gravitational compression and to maintain a steady state.



Eventually, the core exhausts its supply of hydrogen, and without the outward pressure generated by the fusion of hydrogen to counteract the force of gravity, it contracts until either electron degeneracy becomes sufficient to oppose gravity, or the core becomes hot enough (around 100 megakelvins) for helium fusion to begin. Which of these happens first depends upon the star's mass."