Main Sequence Lifetimes

• Once a star is born, how long does it live on the Main Sequence? (OH: Table 9-2)

  • Stays on the main sequence while fusing H to He
  • Eventually, runs out of H in its center (core)
  • Energy generation changes => Leaves MS
  • Stars spend 90% of lifetime on MS
  • More massive stars use up fuel more quickly, so run out of H FIRST! They spend LESS time on the MS! That’s one reason why there are more dim red MS stars than luminous blue MS stars

Notes: