Big bang nucleosynthesis elements
This resulted in the formation of light elements: hydrogen, deuterium, helium two isotopeslithium and trace amounts of beryllium. He suggested to his student, Ralph Alpher, that he calculate this.
If we trust the current models to be basically correct in their prediction that on average, more helium-3 is produced in stars than is destroyed, this gives as an upper limit for the original abundance of helium There just isn't enough time to keep building up to the heavier elements before the neutrons are gone.
Before one neutron half-life passed nearly every neutron had paired up with a proton, and nearly every one of these pairs had paired up to form helium.
How does nucleosynthesis support the big bang theory
More problematic is the lithium During the s, cosmic ray spallation was proposed as a source of deuterium. The answer is supernovae. For younger stars, which have formed from material contaminated with the fusion products of stars of previous generations, the abundances will be different. These are elements with nuclei that are produced by nuclear fusion reactions in stars, but that definitely could not have been produced during Big Bang Nucleosynthesis. One part of his work concerns the evolution of Lithium-plateau stars, which is important for observational tests of the predictions of Big Bang Nucleosynthesis. There are no known post-Big Bang processes which can produce significant amounts of deuterium. In the very early Universe the temperature was so great that all matter was fully ionized and dissociated.
To do that you need stars, which means waiting around for at least billion years. For instance, elements heavier than hydrogen are expected to migrate slowly towards deeper layers of the star, a cosmic analogue to the more familiar phenomenon of sedimentation: if you let a mixture of water and sand settle, the sand will collect at the bottom, following the earth's gravitational pull.
Lithium-7 Finally, and most interesting, there is the abundance of lithium-7 nuclei with 3 protons and 4 neutrons. This is an important and detailed test of nucleosynthesis and is further evidence in support of the Big Bang theory.
Big bang nucleosynthesis for dummies
The more oxygen and nitrogen a region of space contains, the more its light element abundances are bound to have been influenced by stellar nuclear fusion. The shaded areas represent measurements from regions which have a very small abundance of heavy elements, so that they seem to be good samples of primordial abundances. Once deuteron formation has occurred, further reactions proceed to make helium nuclei. The presence of elements such as oxygen or nitrogen see above or, in this particular case, the presence of iron serve as indicators of chemical evolution: Substantial amounts of these elements suggest that a star is young, produced from the debris of other stars. To do that you need stars, which means waiting around for at least billion years. Astronomers have refined this upper limit by looking at an especially well-studied region at a large distance from the galactic centre. If it had been faster, there would be more neutrons and more helium. Using this value, are the BBN predictions for the abundances of light elements in agreement with the observations? The discrepancy is a factor of 2. At this temperature, nucleosynthesis, or the production of light elements, could take place. Burbidge, M.
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