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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.Instead, astronomers need to look for objects in the universe in which, to the best of current knowledge, the abundances of various elements are as close to their primordial value as possible, or which allow extrapolation to the primordial value.
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.
The big bang models - the cosmological models based on general relativity - tell us that the early universe was extremely hot and dense.
By examining how the cooling affects the matter content of the universe, one can derive one of the most impressive testable predictions of the big bang models.
Nuclear Reactions Nucleosynthesis Abundances Essay Cartoon Network
As the universe cools, the matter content changes - new particles are formed out of the preexisting ones, such as protons and neutrons forming out of quarks.
An overview of the results is shown in the following diagram (more detailed plots can be found in the spotlight text Elements of the past): to one for every hundred million, and so on (cf. The vertical axis indicates the different abundances.
For for helium-4, it shows the mass ratio Y (the mass of helium-4 nuclei divided by the total mass of all protons and neutrons in the universe).
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.