Ch 10-02 Helium Burning

• Red Dwarfs: stars of mass between 0.08 M_⊙ and 0.4 M_⊙ cannot ignite helium burning as described below. Strong convection gradually turns all the hydrogen into helium in the whole star. Their surface temperature is low. They are called red dwarfs.
  
  
• The triple-alpha process, to occur for stars heavier than 0.4 M_⊙
  
  
  
  
• Helium core burning + hydrogen shell burning
  
  
  [After igniting helium, the core expands and outer layers contract.]
  
  
• The horizontal branch
  
  
  [Solar-mass stars reside in the area 'clump' during helium core burning, typically for 1% of their main-sequence life time.]
  
  
  
  
• Degeneracy pressure; helium flash (for mass less than 2~3 solar masses)