CNO-I cycle The helium nucleus is released at the top-left step.
CNO-I cycle The helium nucleus is released at the top-left step. Hydrogen fusion nuclear fusion of four protons to form a helium-4 nucleus  is the dominant process that generates energy in the cores of main-sequence stars.
It is also called "hydrogen burning", which should not be confused with the chemical combustion of hydrogen in an oxidizing atmosphere.
There are two predominant processes by which stellar hydrogen fusion occurs: Ninety percent of all stars, with the exception of white dwarfsare fusing hydrogen by these two processes.
In the cores of lower-mass main-sequence stars such as the Sunthe dominant energy production process Elements formed in stellar nucleosynthesis the proton—proton chain reaction. This creates a helium-4 nucleus through a sequence of chain reactions that begin with the fusion of two protons to form a deuterium nucleus one proton plus one neutron along with an ejected positron and neutrino.
In higher-mass stars, the dominant energy production process is the CNO cyclewhich is a catalytic cycle that uses nuclei of carbon, nitrogen and oxygen as intermediaries and in the end produces a helium nucleus as with the proton-proton chain. The difference in energy production of this cycle, compared to the proton—proton chain reaction, is accounted for by the energy lost through neutrino emission.
As a result, the core region becomes a convection zonewhich stirs the hydrogen fusion region and keeps it well mixed with the surrounding proton-rich region. The type of hydrogen fusion process that dominates in a star is determined by the temperature dependency differences between the two reactions.
This temperature is achieved in the cores of main sequence stars with at least 1. As a main sequence star ages, the core temperature will rise, resulting in a steadily increasing contribution from its CNO cycle.
Triple-alpha process and Alpha process Main sequence stars accumulate helium in their cores as a result of hydrogen fusion, but the core does not become hot enough to initiate helium fusion. Helium fusion first begins when a star leaves the red giant branch after accumulating sufficient helium in its core to ignite it.
In stars around the mass of the sun, this begins at the tip of the red giant branch with a helium flash from a degenerate helium core and the star moves to the horizontal branch where it burns helium in its core. More massive stars ignite helium in their cores without a flash and execute a blue loop before reaching the asymptotic giant branch.
Despite the name, stars on a blue loop from the red giant branch are typically not blue in color, but are rather yellow giants, possibly Cepheid variables. They fuse helium until the core is largely carbon and oxygen. The most massive stars become supergiants when they leave the main sequence and quickly start helium fusion as they become red supergiants.
After helium is exhausted in the core of a star, it will continue in a shell around the carbon-oxygen core. This can then form oxygen, neon, and heavier elements via the alpha process. In this way, the alpha process preferentially produces elements with even numbers of protons by the capture of helium nuclei.Stage 8: Planetary Nebula or Supernova Chapter index in this window — — Chapter index in separate window This material (including images) is copyrighted!.See my copyright notice for fair use practices.
Select the photographs to display the original source in another window. Stellar Nucleosynthesis: Where Did Heavy Elements Come From? BY VERNON R. CUPPS for the r-process as neutrons, come from? And the ubiquitous question remains, how much was already there and how much formed from the collision?
Figure 1. Principles of Stellar Evolution and Nucleosynthesis. Chicago: University of Chicago Press, A Discussion of Stellar Nucleosynthesis Answers Research Journal 7 ()– polarities present where the spectral lines are formed. elements formed. The only discussion of this theory in the creation literature thus far is that of Wilt ().
In this paper I expand upon that discussion. Stellar Nucleosynthesis Chapter index in this window — — Chapter index in separate window This material (including images) is copyrighted!.See my copyright notice for fair use practices..
Hydrogen and helium and some lithium, boron, and beryllium were created when the universe was created. See the UVS topic on "The hyperspheric pushed-in gravity" that elaborates on the causality for the mass effect of rutadeltambor.com cognitive paradox that renders the obscured observation for the structure of atom, could thus be meticulously resolved with its underlying structure and mechanism illustrated.
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