This is consistent with the standard or " big bang " model. The process of forming the hydrogen and helium and other trace constituents is often called " big bang nucleosynthesis ". This high percentage of helium argues strongly for the big bang model, since other models gave very small percentages of helium.
However, the lack of stable nuclei with atomic weights of 5 or 8 limited the Big Bang to producing hydrogen and helium. But BBFH could not produce enough helium.
Now we know that both processes occur: Most lithium and beryllium is produced by cosmic ray collisions breaking up some of the carbon produced in stars. The following stages occur during the first few minutes of the Universe: Less than 1 second after the Big Bang, the reactions shown at right maintain the neutron: About 1 second after the Big Bang, the temperature is slightly less than the neutron-proton mass difference, these weak reactions become slower than the expansion rate of the Universe, and the neutron: After 1 second, the only reaction that appreciably changes the number of neutrons is neutron decay, shown at right.
The half-life of the neutron is seconds. Without further reactions to preserve neutrons within stable nuclei, the Universe would be pure hydrogen. The reaction that preserves the neutrons is deuteron formation. The deuteron is the nucleus of deuterium, which is the heavy form of hydrogen H2.
This reaction is exothermic with an energy difference of 2. At this time, the neutron: Once deuteron formation has occurred, further reactions proceed to make helium nuclei. Both light helium He3 and normal helium He4 are made, along with the radioactive form of hydrogen H3.
These reactions can be photoreactions as shown here. The reactions at right also produce helium and usually go faster since they do not involve the relatively slow process of photon emission. The net effect is shown at right. Eventually the temperature gets so low that the electrostatic repulsion of the deuterons causes the reaction to stop.
Almost all the neutrons in the Universe end up in normal helium nuclei. The mass fraction in various isotopes vs time is shown at right. Deuterium peaks around seconds after the Big Bang, and is then rapidly swept up into helium nuclei.
A very few helium nuclei combine into heavier nuclei giving a small abundance of Li7 coming from the Big Bang. This graph is a corrected version of one from this LBL page. Note that H3 decays into He3 with a 12 year half-life so no H3 survives to the present, and Be7 decays into Li7 with a 53 day half-life and also does not survive.
The graph above shows the time evolution of the abundances of the light elements for a slightly higher baryon density.
The deuterium, He3, He4 and Li7 abundances depend on the single parameter of the current density of ordinary matter made out of protons and neutrons: The graph above shows the predicted abundance vs.
A single value of the baryon density fits 4 abundances simultaneously. The fit is good but not perfect. There has been a dispute about the actual primordial helium abundance in the Universe: And a new measurement of the free neutron lifetime is 6 sigma smaller that the previous world average, giving a new prediction of the helium abundance of The observed lithium abundance in stars is less than the predicted lithium abundance, by a factor of about 2.
But stars destroy lithium so it is hard to assess the significance of this difference.Big Bang Nucleosynthesis Gamow, Alpher and Herman proposed the hot Big Bang as a means to produce all of the elements. However, the lack of stable nuclei with atomic weights of 5 or 8 limited the Big Bang to producing hydrogen and helium.
33 rows · Discussion big bang nucleosynthesis. By the first millisecond, the universe had cooled to . Stellar nucleosynthesis is the process by which elements are created within stars by combining the protons and neutrons together from the nuclei of lighter elements. All of the atoms in the universe began as hydrogen. Big Bang Nucleosynthesis Gamow, Alpher and Herman proposed the hot Big Bang as a means to produce all of the elements. However, the lack of stable nuclei with atomic weights of 5 or 8 limited the Big Bang to producing hydrogen and helium.
The relativistic ideas behind this spotlight topic are explained in Elementary Einstein, especially in the chapter Cosmology..
For more information about Big Bang Nucleosynthesis, check out the spotlight texts Equilibrium and Change: The physics behind Big Bang Nucleosynthesis and Elements of the past: Reconstructing . Big-Bangnucleosynthesis 3 Figure The abundances of 4He, D, 3He, and 7Li as predicted by the standard model of Big-Bang nucleosynthesis — the bands show the 95% CL range.
Boxes indicate the observed light element abundances. Big Bang Nucleosynthesis The Universe's light-element abundance is another important criterion by which the Big Bang hypothesis is verified. It is now known that the elements observed in the Universe were created in either of two ways.
Big Bang Nucleosynthesis The emergence of elements in the universe Benjamin Topper Abstract. In this paper, I will first give a brief overview of .
Apr 16, · The term nucleosynthesis refers to the formation of heavier elements, atomic nuclei with many protons and neutrons, from the fusion of lighter elements.
The Big Bang theory predicts that the early universe was a very hot place.