More massive stars burn their nuclear fuel more quickly, since they have to offset greater gravitational forces to stay in (approximate) hydrostatic equilibrium.
[6] The first two reactions are strongly exothermic, as indicated by the large positive energies released, and are the most frequent results of the interaction.
[6] In stars between 4 and 11 solar masses, the 16O already produced by helium fusion in the previous stage of stellar evolution manages to survive the carbon-burning process pretty well, despite some of it being used up by capturing 4He nuclei.
Neutrino losses start to become a major factor in the fusion processes in stars at the temperatures and densities of carbon burning.
But the main source of neutrinos at these high temperatures involves a process in quantum theory known as pair production.
Neutrino losses, by this and similar processes, play an increasingly important part in the evolution of the most massive stars.
[2] Fusion processes are very sensitive to temperature so the star can produce more energy to retain hydrostatic equilibrium, at the cost of burning through successive nuclear fuels ever more rapidly.
In successive fuel changes in the most massive stars, the reduction in lifetime is dominated by the neutrino losses.
The inert core eventually reaches sufficient mass to collapse due to gravitation, whilst the helium burning moves gradually outward.
[12] Stars of below 4 solar masses never reach high enough core temperature to burn carbon, instead ending their lives as carbon-oxygen white dwarfs after shell helium flashes gently expel the outer envelope in a planetary nebula.
[14] In the late stages of this nuclear burning they develop a massive stellar wind, which quickly ejects the outer envelope in a planetary nebula leaving behind an O-Ne-Na-Mg white dwarf core of about 1.1 solar masses.