core largely carbon oxygen massive stars become supergiants leave main sequence quickly start helium fusion become red supergiants helium exhausted core star continue shell around carbon oxygen core ref name jones ref name deloore doom cases helium fused carbon via triple alpha process ie three helium nuclei transformed carbon via sup sup form oxygen neon heavier elements via alpha process way alpha process preferentially produces elements even numbers
Natural science Space science Stellar astrophysics Stellar nucleosynthesis