Carbon nitrogen oxygen cycle

The process by which a star converts hydrogen into helium

Collection

zero Useful+1

zero

The carbon nitrogen oxygen cycle (carbon nitrogen oxygen), sometimes called the Bess Weitzzek cycle, is fixed star take hydrogen convert to helium One of the two processes of Proton proton chain Reaction.

Chinese name: Carbon nitrogen oxygen cycle
Foreign name: CNO cycle

Alias: Beth Weitzzek cycle
Element: Carbon, nitrogen, oxygen
Definition: fixed star take hydrogen convert to helium One of the two processes of

catalog

Specific reactions

Announce

edit

In stars with masses like the sun or smaller, Proton proton chain reaction Is the main process of generating energy. The sun has only 1.7% four The He core is generated through the carbon nitrogen oxygen cycle, but the theoretical model shows that Heavier stars generate energy mainly from the carbon nitrogen oxygen cycle 。 The process of carbon nitrogen oxygen cycle is composed of Carl von Weizsäcker and Hans Bate They were put forward independently in 1938 and 1939 respectively.

The reaction of carbon nitrogen oxygen cycle is as follows:

twelve C + one H → thirteen N + γ +1.95 MeV

thirteen N → thirteen C + e + + ν e +2.22 MeV

thirteen C + one H → fourteen N + γ +7.54 MeV

fourteen N + one H → fifteen O + γ +7.35 MeV

fifteen O → fifteen N + e + + ν e +2.75 MeV

fifteen N + one H → twelve C + four He +4.96 MeV

The net effect of this cycle is 4 proton Become a Alpha particle , 2 positron (and Electronics Annihilation to Gamma ray And two neutrinos carrying part of the energy escaped from the star. Carbon, nitrogen, and oxygen nuclei act as catalysts and regenerate in the cycle.

exceptional case

Announce

edit

In special cases, there is a small branch reaction, which only accounts for 0.04% of the total amount in the solar core. The final product is not 12 carbon and 4 helium, but 16 oxygen and a photon. The replacement process is as follows:

fifteen N + one H → sixteen O + γ +12.13 MeV

sixteen O + one H → seventeen F + γ +0.60 MeV

seventeen F → seventeen O +e + + ν e +2.76 MeV

seventeen O + one H → fourteen N + four He +1.19 MeV

Effect of fluorine

Announce

edit

Similarly, carbon, nitrogen, and oxygen are in the main branch, while in the smaller branch fluorine It is only a catalyst in a stable state and will not accumulate in the star.

III Branch

Announce

edit

The main branch of the carbon nitrogen oxygen cycle is called carbon nitrogen oxygen I, and the small branch is called carbon nitrogen oxygen II. In the heavier stars, there are two secondary main branches, carbon nitrogen oxygen III and carbon nitrogen oxygen IV, which begin at the final stage of the carbon nitrogen oxygen II reaction, and result in the replacement of the original 14 nitrogen and helium nuclei with 18 oxygen and gamma rays

III Branch reaction:

seventeen O + one H → eighteen F

eighteen F → eighteen O +e + + ν e + γ

IV Branch

Announce

edit

seventeen O + one H → eighteen F + γ +5.61 MeV

eighteen F → eighteen O + e + + v e +1.656 MeV

eighteen O+ one H → nineteen F + γ +7.994 MeV

nineteen F + one H → sixteen O + four He +8.114MeV

sixteen O+ one H → seventeen F + γ +0.6MeV

seventeen F → seventeen O + e + + v e +2.76MeV

Schematic diagram of carbon nitrogen oxygen cycle

Here, the number of all "catalysts" (carbon, nitrogen and oxygen nuclei) involved in the reaction is conserved, and the relative proportion of nuclei will change in the evolution of stars. No matter what the initial structure is, when the cycle is in equilibrium, twelve Carbon/ thirteen The proportion of carbon nuclei is 3.5, while fourteen Nitrogen became the most abundant nucleus. In the evolution of stars, convection will bring the products of carbon, nitrogen and oxygen cycle from the interior of stars to the surface and mix, changing the observed stellar composition. In red giant stars, compared with Main sequence star , a small amount of twelve Carbon/ thirteen Carbon and twelve Carbon/ fourteen Nitrogen, all of which can prove that hydrogen fuses in the interior of stars for energy generation alternation.

Novice on the road

Growth task Getting Started with Editing Edit Rule Edit by myself

I have questions

Content query Online Service Official post bar Feedback

Complaints and suggestions

Report bad information Failed to appeal through entries Complaint of infringement information Blocking query and unblocking

Jinggong Network Anbei No. 1100000200001