Nuclear Reactions Nucleosynthesis Abundances

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The network includes, at any given time, all relevant isotopes from hydrogen through polonium (Z=84).

Even the limited grid of stellar masses studied suggests that overall good agreement can be achieved with the solar abundances of nuclei between model and (so far, only in that model) are a consequence of the merging of the oxygen, neon, and carbon shells about a day prior to core collapse.

While the abundance predictions have traditionally been used to fix the correct value for eta, there are different possibilities for measuring that number.

Most notably, the presence of particles like protons and neutrons in the early universe leaves a slight, but measurable imprint on the cosmic background radiation.

From about one second to a few minutes cosmic time, when the temperature has fallen below 10 billion Kelvin, the conditions are just right for protons and neutrons to combine and form certain species of atomic nuclei. While the early universe is totally unlike our everyday world, the basic nuclear physics at the appropriate energies is well within the range of laboratory experiments.

Following such experiments, the properties of the relevant nuclear reactions are very well known.Calculations are performed for Population I stars of 15, 19, 20, 21, and 25 M using the most recently available experimental and theoretical nuclear data, revised opacity tables, neutrino losses, and weak interaction rates and taking into account mass loss due to stellar winds.A novel ``adaptive'' reaction network is employed with a variable number of nuclei (adjusted each time step) ranging from ~700 on the main sequence to ~2200 during the explosion.For the other nuclei, it shows the number of such nuclei, divided by the number nuclei of hydrogen, the most abundant element.The curves indicate the theoretical predictions from Big Bang nucleosynthesis, the horizontal stripes the values that follow from observations.By mass, about a quarter of the nuclei in the universe should be helium-4.Deuterium, tritium, helium-3 and lithium-7 nuclei should occur in much smaller, but still measurable quantities.Big Bang Nucleosynthesis was incapable to produce heavier atomic nuclei such as those necessary to build human bodies or a planet like the earth.Instead, those nuclei were formed in the interior of stars.To learn more or modify/prevent the use of cookies, see our Cookie Policy and Privacy Policy.The big bang models - the cosmological models based on general relativity - tell us that the early universe was extremely hot and dense.


Comments Nuclear Reactions Nucleosynthesis Abundances

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