Hydrogen and helium fusion pathways in stars
The proton–proton chains and CNO cycles convert hydrogen into helium through different reaction sequences; CNO nuclei participate in a catalytic cycle.
Key knowledge
The proton–proton chains and CNO cycles convert hydrogen into helium through different reaction sequences; CNO nuclei participate in a catalytic cycle. Helium burning can form carbon through the triple-alpha sequence. Rates and pathway contributions depend on temperature, density and composition, and neutrinos carry away part of the released energy.
Conditions and scope
- A shorthand net hydrogen-to-helium equation must include the leptons and energy accounting of its actual sequence.
- These are representative stellar pathways; they do not imply that all heavier elements originate in one class of explosion.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read pathway text and neutrino-loss discussion; did not copy misprinted CNO isotope subscripts, fixed illustrative percentages or a mass-only boundary between dominant pathways.
2026-10-10 · Independent AI editorial review: All26 Life-authored Cosmos compact statements, conditions, displayed equations and all56 origin semantic links read. Entire26-entry author statement/source matrix and explicit exclusions assessed. Targeted independent primary sections are listed below; this does not claim every referenced source body or proof was independently re-read. This is scoped AI reference-content review, not human disciplinary certification or whole-field completion. Receipt: cosmos-life-independent-content-review.1.
Entry details
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- University core expansion