Energy Sources in Stars (§10.3)
Energy Sources in Stars (§10.3)
Energy Sources in Stars (§10.3)
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Alternate Fusion Reactions H → 4 HeCNO Cycle (or bi-cycle)• First step <strong>in</strong> PP cha<strong>in</strong> has very lowreaction rate (weak <strong>in</strong>teraction).• 12 C can act as a catalyst <strong>in</strong> fusionreaction.• Net result:12 C + 4p + → 12 C + 4 He + 2e + + 2ν2+ 3γ3• Note: 12 C neither created nordestroyed. Also isotopes of N & Oare temporarily produced.• CNO cycle dom<strong>in</strong>ates over PPcha<strong>in</strong> if T core > 1.8 x 10 7 (slightlyhotter than Sun)THE CNO BI-CYCLE(T < 10 8 K)10 6 yr}14 m<strong>in</strong>3 x 10 5 yr3 x 10 8 yr82 s10 4 yrX as frequentlyOnce forevery 2500<strong>in</strong>stances ofCycle 1
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