Introduction to Geochemistry

Nucleosynthesis in massive stars
! The CNO cycle is the dominant mechanism of nucleosynthesis in
stars heavier than the Sun (1.5 solar mass and up)
Step 1: 12 C + 1 H
13 N + $
Step 2: 13 N
13 C + # + + "
Step 3: 13 C + 1 H
14 N + $
Step 4: 14 N + 1 H
15 O + $
Step 5: 15 O # + + " + N
Step 6:
15 N + 1 H
12 C + 4 He
Overall:
4 protons form one He, C acts as a catalyst…