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Thread: Question regarding nuclear fusion in a star

  1. #1 Fusion inside a Giant Star and the speed of light 
    The Doctor Quantime's Avatar
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    I'm wondering say in stars such as VY Canis Majoris and in other super/hypergiants alike, what determines the nuclear fusion process at say the core of the star and at halfway out of the radius of the star, taking into consideration the speed of light.

    Does this have any effect on the star? Say the sun as a main sequence star a fusion reaction at one part of the star and another at another point the distance in time between the two would be seconds right? So what if this is hours? Is there an effect?


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  3. #2 Question regarding nuclear fusion in a star 
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    Does nuclear fusion of Carbon and Oxygen produce more energy than fusion of Deuterium and Tritium?


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    The speed of light is irrelevant (more or less). The fusion process is controlled by density, temperature and pressure.

    Even for a star like our sun, it is estimated that in takes 10,000 to 170,000 years for a photon to make it from the core to the light emitting surface due to constant absorbtion and reemission.
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    Merged two almost identical threads.
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  6. #5  
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    Based on this, I'd say the answer is no.

    The Astrophysics Spectator: Hydrogen Fusion in Stars
    The Proton-Proton ProcessThere are three branches to the PP process of convert hydrogen (H1) into helium (He4). The first branch does the conversion without creating any nuclei heavier than helium. The remaining two branches go through a step that creates beryllium.
    ...
    The total energy released in converting four hydrogen nuclei into a single Helium nucleus is the same for each of the three branches, 26.7 MeV.
    The Astrophysics Spectator: The Fusion of Carbon and Oxygen in Stars

    In the carbon-fusion stage, two carbon-12 nuclei fuse to create heavier elements. Carbon preferentially interacts only with itself, unlike helium, which interacts with heavy elements such as carbon-12 and oxygen-16. In particular, there is no appreciable interaction between carbon-12 and oxygen-16. The primary nuclei created through carbon fusion are sodium-23 (Na23) and neon-20 (Ne20).
    Carbon fusion begins at about 600 to 700 million degrees (50 to 60 keV). The most energetic carbon-carbon reaction liberates approximately 13 MeV of energy as magnesium-24 (Mg24) is created. Other carbon-carbon reactions liberate considerably less energy than this, and in some cases consuming energy.
    In oxygen fusion, two oxygen nuclei fuse to create elements with atomic mass at or below the mass of sulfur-32. Many different nuclei are created in this process, although silicon-28 (Si28) is the the major product from the nuclear fusion of oxygen. Oxygen fusion begins at about 1 billion degrees (90 keV). The energy released is more uncertain than for the carbon burning, but it is comparable in value.
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