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  2. Helium-4 - Wikipedia

    en.wikipedia.org/wiki/Helium-4

    The stability of helium-4 is the reason that hydrogen is converted to helium-4, and not deuterium (hydrogen-2) or helium-3 or other heavier elements during fusion reactions in the Sun. It is also partly responsible for the alpha particle being by far the most common type of baryonic particle to be ejected from an atomic nucleus; in other words ...

  3. Big Bang nucleosynthesis - Wikipedia

    en.wikipedia.org/wiki/Big_Bang_nucleosynthesis

    "One analogy is to think of helium-4 as ash, and the amount of ash that one forms when one completely burns a piece of wood is insensitive to how one burns it." [16] The resort to the BBN theory of the helium-4 abundance is necessary as there is far more helium-4 in the universe than can be explained by stellar nucleosynthesis. In addition, it ...

  4. Nucleosynthesis - Wikipedia

    en.wikipedia.org/wiki/Nucleosynthesis

    The subsequent nucleosynthesis of heavier elements (Z ≥ 6, carbon and heavier elements) requires the extreme temperatures and pressures found within stars and supernovae. These processes began as hydrogen and helium from the Big Bang collapsed into the first stars after about 500 million years.

  5. Triple-alpha process - Wikipedia

    en.wikipedia.org/wiki/Triple-alpha_process

    As a side effect of the process, some carbon nuclei fuse with additional helium to produce a stable isotope of oxygen and energy: 12 6 C + 4 2 He → 16 8 O + γ (+7.162 MeV) Nuclear fusion reactions of helium with hydrogen produces lithium-5, which also is highly unstable, and decays back into smaller nuclei with a half-life of 3.7 × 10 −22 s.

  6. Supernova nucleosynthesis - Wikipedia

    en.wikipedia.org/wiki/Supernova_nucleosynthesis

    Supernova nucleosynthesis is the nucleosynthesis of chemical elements in supernova explosions.. In sufficiently massive stars, the nucleosynthesis by fusion of lighter elements into heavier ones occurs during sequential hydrostatic burning processes called helium burning, carbon burning, oxygen burning, and silicon burning, in which the byproducts of one nuclear fuel become, after ...

  7. Alpha process - Wikipedia

    en.wikipedia.org/wiki/Alpha_process

    The other class is a cycle of reactions called the triple-alpha process, which consumes only helium, and produces carbon. [1] The alpha process most commonly occurs in massive stars and during supernovae. Both processes are preceded by hydrogen fusion, which produces the helium that fuels both the triple-alpha process and the alpha ladder ...

  8. Proton–proton chain - Wikipedia

    en.wikipedia.org/wiki/Proton–proton_chain

    Once the helium-3 has been produced, there are four possible paths to generate 4 He. In p–p I, helium-4 is produced by fusing two helium-3 nuclei; the p–p II and p–p III branches fuse 3 He with pre-existing 4 He to form beryllium-7, which undergoes further reactions to produce two helium-4 nuclei. About 99% of the energy output of the sun ...

  9. Radioactive decay - Wikipedia

    en.wikipedia.org/wiki/Radioactive_decay

    Any decay daughters that are the result of an alpha decay will also result in helium atoms being created. Some radionuclides may have several different paths of decay. For example, 35.94(6) % [ 27 ] of bismuth-212 decays, through alpha-emission, to thallium-208 while 64.06(6) % [ 27 ] of bismuth-212 decays, through beta-emission, to polonium-212 .