Step 1: Proton Fusion
p + p → d + e⁺ + νₑ
PP Chain Branches
PP-I Chain
~83% in Sun • 26.2 MeV
PP-II Chain
~17% in Sun • via ⁷Be
PP-III Chain
~0.02% in Sun • via ⁸B
Energy per cycle:
26.7 MeV
4p → ⁴He + 2e⁺ + 2νₑ
Solar Core: T ≈ 15 million K
Rate: ~3.6×10³⁸ reactions/sec
Power: 3.8×10²⁶ W (99% from pp-chain)
The first step (p+p → d) is rate-limiting, taking ~10⁹ years on average!
Rate: ~3.6×10³⁸ reactions/sec
Power: 3.8×10²⁶ W (99% from pp-chain)
The first step (p+p → d) is rate-limiting, taking ~10⁹ years on average!