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- CNO_cycle abstract "The CNO cycle (for carbon–nitrogen–oxygen) is one of two sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton–proton chain reaction. Unlike the latter, the CNO cycle is a catalytic cycle. Theoretical models show that the CNO cycle is the dominant source of energy in stars more massive than about 1.3 times the mass of the Sun. The proton–proton chain is more important in stars the mass of the Sun or less. This difference stems from temperature dependency differences between the two reactions; pp-chain reactions start occurring at temperatures around 4×106 K (4 megakelvins), making it the dominant energy source in smaller stars. A self-maintaining CNO chain starts occurring at approximately 15 MK, but its energy output rises much more rapidly with increasing temperatures. At approximately 17 MK, the CNO cycle starts becoming the dominant source of energy. The Sun has a core temperature of around 15.7 MK, and only 1.7% of 4He nuclei being produced in the Sun are born in the CNO cycle. The CNO-I process was independently proposed by Carl von Weizsäcker and Hans Bethe in 1938 and 1939, respectively.In the CNO cycle, four protons fuse, using carbon, nitrogen and oxygen isotopes as a catalyst, to produce one alpha particle, two positrons and two electron neutrinos. Although there are various paths and catalysts involved in the CNO cycles, simply speaking all these cycles have the same net result:4 11H + 2 e− → 42He + 2 e+ + 2 e− + 2 νe + 3 γ + 24.7 MeV → 42He + 2 νe + 3 γ + 26.7 MeVThe positrons will almost instantly annihilate with electrons, releasing energy in the form of gamma rays. The neutrinos escape from the star carrying away some energy. One nucleus goes to become carbon, nitrogen, and oxygen isotopes through a number of transformations in an endless loop.".
- CNO_cycle thumbnail CNO_Cycle.svg?width=300.
- CNO_cycle wikiPageID "6061".
- CNO_cycle wikiPageRevisionID "594808183".
- CNO_cycle hasPhotoCollection CNO_cycle.
- CNO_cycle subject Category:Nuclear_fusion.
- CNO_cycle comment "The CNO cycle (for carbon–nitrogen–oxygen) is one of two sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton–proton chain reaction. Unlike the latter, the CNO cycle is a catalytic cycle. Theoretical models show that the CNO cycle is the dominant source of energy in stars more massive than about 1.3 times the mass of the Sun. The proton–proton chain is more important in stars the mass of the Sun or less.".
- CNO_cycle label "Bethe-Weizsäcker-Zyklus".
- CNO_cycle label "CNO cycle".
- CNO_cycle label "CNO-цикл".
- CNO_cycle label "CNOサイクル".
- CNO_cycle label "Ciclo CNO".
- CNO_cycle label "Ciclo CNO".
- CNO_cycle label "Ciclo del carbonio-azoto".
- CNO_cycle label "Cycle carbone-azote-oxygène".
- CNO_cycle label "Cykl węglowo-azotowo-tlenowy".
- CNO_cycle label "Koolstof-stikstofcyclus".
- CNO_cycle label "دورة كربون-نيتروجين-أكسجين".
- CNO_cycle label "碳氮氧循環".
- CNO_cycle sameAs CNO_cyklus.
- CNO_cycle sameAs Bethe-Weizsäcker-Zyklus.
- CNO_cycle sameAs Ciclo_CNO.
- CNO_cycle sameAs Cycle_carbone-azote-oxygène.
- CNO_cycle sameAs Siklus_CNO.
- CNO_cycle sameAs Ciclo_del_carbonio-azoto.
- CNO_cycle sameAs CNOサイクル.
- CNO_cycle sameAs CNO_순환.
- CNO_cycle sameAs Koolstof-stikstofcyclus.
- CNO_cycle sameAs Cykl_węglowo-azotowo-tlenowy.
- CNO_cycle sameAs Ciclo_CNO.
- CNO_cycle sameAs m.01tkh.
- CNO_cycle sameAs Q222971.
- CNO_cycle sameAs Q222971.
- CNO_cycle wasDerivedFrom CNO_cycle?oldid=594808183.
- CNO_cycle depiction CNO_Cycle.svg.
- CNO_cycle isPrimaryTopicOf CNO_cycle.
