The CNO (carbon-nitrogen-oxygen) cycle is one of two fusion reactions by which stars convert hydrogen to helium, the other being the proton-proton chain. While the proton-proton chain is more important in stars the size of the sun or less, theoretical models show that the CNO cycle is the dominant source of energy in heavier stars. The CNO process was proposed in 1938 by Hans Bethe. General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... In nuclear physics, a nuclear reaction is a process in which two nuclei or nuclear particles collide, to produce products different to the initial products. ... The Pleiades star cluster A star is a massive body of plasma in outer space that is currently producing or has produced energy through nuclear fusion. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ... The proton-proton chain reaction is one of two fusion reactions by which stars convert hydrogen to helium, the other being the CNO cycle. ... The Sun (or Sol) is the star at the center of our Solar system. ... 1938 (MCMXXXVIII) was a common year starting on Saturday (link will take you to calendar). ... Hans Bethe Hans Albrecht Bethe (pronounced Bay-tuh; July 2, 1906 – March 6, 2005), was a German-American physicist who won the Nobel Prize in Physics for 1967 for his discovery of stellar nucleosynthesis. ...

The reactions of the CNO cycle are:

12C + 1H	→	13N + γ	+1,95 MeV
13N	→	13C + e+ + νe	+1,37 MeV
13C + 1H	→	14N + γ	+7,54 MeV
14N + 1H	→	15O + γ	+7,35 MeV
15O	→	15N + e+ + νe	+1,86 MeV
15N + 1H	→	12C + 4He	+4,96 MeV

The net result of the cycle is to fuse four protons into an alpha particle plus two positrons and two neutrinos, releasing energy in the form of gamma rays. The carbon, oxygen, and nitrogen nuclei serve as catalysts and are regenerated. This article is about electromagnetic radiation. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... The neutrino is an elementary particle. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... An alpha particle is deflected by a magnetic field Alpha particles or alpha rays are a form of particle radiation which are highly ionizing and have low penetration. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... The neutrino is an elementary particle. ... This article is about electromagnetic radiation. ... A catalyst (Greek: καταλύτης, catalytēs) is a substance that accelerates the rate (speed) of a chemical reaction without itself being transformed or consumed by the reaction (see also catalysis). ...

In a minor branch of the reaction, occurring just 0.04% of the time, the final reaction shown above does not produce ¹²C and ⁴He, but instead produces ¹⁶O and a photon and continues as follows:

15N + 1H	→	16O + γ
16O + 1H	→	17F + γ
17F	→	17O + e+ + νe
17O + 1H	→	14N + 4He

Like the carbon, nitrogen, and oxygen involved in the main branch, the fluorine produced in the minor branch is merely catalytic and at steady state, does not accumulate in the star.

See also

• Triple-alpha process
• Proton-proton chain