Please help improve this section by adding citations to reliable sources. Big Bang nucleosynthesis Big Bang nucleosynthesis  occurred within the first three minutes of the beginning of the universe and is responsible for much of the abundance of 1H protium2H D, deuterium3He helium-3and 4He helium Further details can be found here.
This first process, Big Bang nucleosynthesiswas the first type of nucleogenesis to occur in the universe. To begin with, it was estimated that only a small amount of matter found in the Universe should consist of helium if stellar nuclear reactions were its only source of production.
The major types of nucleosynthesis[ edit ] Big Bang nucleosynthesis[ edit ] Main article: Star formation has occurred continuously in galaxies since that time.
In terms Primordial nucleosynthesis helium the present day critical density of matter, the required density of baryons is a few percent the exact value depends on the assumed value of the Hubble constant.
That fusion process essentially shut down at about 20 minutes, due to drops in temperature and density as the universe continued to expand. This has been done to put limits on the mass of a stable tau neutrino.
At this temperature, nucleosynthesis, or the production of light elements, could take place.
In the years immediately before World War II, Hans Bethe first elucidated those nuclear mechanisms Primordial nucleosynthesis helium which hydrogen is fused into helium.
Elements from carbon up to sulfur may be made in small stars by the alpha process. The majority of these occur in within stars, and the chain of those nuclear fusion processes are known as hydrogen burning via the proton-proton chain or the CNO cyclehelium burningcarbon burningneon burningoxygen burning and silicon burning.
At this temperature, nucleosynthesis, or the production of light elements, could take place. Hydrogen and helium are most common, residuals within the paradigm of the Big Bang.
This section does not cite any sources. The temperatures, time, and densities were sufficient to combine a substantial fraction of the deuterium nuclei to form helium-4 but insufficient to carry the process further using helium-4 in the next fusion step.
See Handbook of Isotopes in the Cosmos for more data and discussion of abundances of the isotopes. Elements heavier than iron may be made in neutron star mergers or supernovae after the r-processinvolving a dense burst of neutrons and rapid capture by the element.
This relatively low value means that not all of the dark matter can be baryonic, ie we are forced to consider more exotic particle candidates.
Primordial nucleosynthesis helium present measurement of helium-4 indicates good agreement, and yet better agreement for helium Both theory and observation lead astronomers to believe this to be the case. Learn More in these related Britannica articles: Further details can be found here.
A similar enigma exists Primordial nucleosynthesis helium the deuterium. Specifically, the theory yields precise quantitative predictions for the mixture of these elements, that is, the primordial abundances at the end of the big-bang.
A star gains heavier elements by combining its lighter nuclei, hydrogendeuteriumberylliumlithiumand boronwhich were found in the initial composition of the interstellar medium and hence the star.
Thanks to the pioneering efforts of George Gamow and his collaborators, there now exists a satisfactory theory as to the production of light elements in the early Universe. Elements formed during this time were in the plasma state, and did not cool to the state of neutral atoms until much later. Many of the chemical elements up to iron atomic number 26 and their present cosmic abundances may be accounted for by successive nuclear fusion reactions beginning with hydrogen and perhaps some primeval helium.
Although 4He continues to be produced by stellar fusion and alpha decays and trace amounts of 1H continue to be produced by spallation and certain types of radioactive decay, most of the mass of the isotopes in the universe are thought to have been produced in the Big Bang.
The problem here again is that deuterium is very unlikely due to nuclear processes, and that collisions between atomic nuclei are likely to result either in the fusion of the nuclei, or in the release of free neutrons or alpha particles.
During the s, there were major efforts to find processes that could produce deuterium, but those revealed ways of producing isotopes other than deuterium. The subsequent nucleosynthesis of the heavier elements requires the extreme temperatures and pressures found within stars and supernovas.
These should not be confused with non-standard cosmology: These processes began as hydrogen and helium from the Big Bang collapsed into the first stars at million years.The Big Bang Nucleosynthesis theory predicts that roughly 25% the mass of the Universe consists of Helium.
It also predicts about % deuterium, and even smaller quantities of lithium. The important point is that the prediction depends critically on the density of baryons (ie neutrons and protons) at the time of nucleosynthesis. The primordial nucleosynthesis, however, faces some controverses.
As an example, it is considered now that lithium can also be produced in the stars, and the primordial. Primordial Nucleosynthesis By GARY STEIGMAN Department of Physics, The Ohio State University, Columbus, OHUSA The primordial abundances of deuterium, helium-3, helium-4, and lithium-7 probe the baryon density of the Universe only a few minutes after the Big Bang.
Of. In physical cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than H-1, the normal, light hydrogen, during the early phases of the. Primordial nucleosynthesis was the production of elements heavier than Hydrogen soon after the Big Bang.
Soon after the Big Bang the Universe was filled with mainly Hydrogen in the form of protons and neutrons. The conditions were then right for fusion reactions to occur.
These produced the Hydrogen isotopes Deuterium and Tritium and Helium 3 and helium 4. Primordial nucleosynthesis was the production of elements heavier than Hydrogen soon after the Big Bang. Soon after the Big Bang the Universe was filled with mainly Hydrogen in the form of protons and neutrons.
The conditions were then right for fusion reactions to occur.
These produced the Hydrogen isotopes Deuterium and Tritium and Helium 3 and helium 4.Download