Big Bang Nucleosynthesis The Universe's light-element abundance is another important criterion by which the Big Bang hypothesis is verified.
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.Big-Bangnucleosynthesis 1 BIG-BANGNUCLEOSYNTHESIS Revised August by B.D.
Fields (Univ. of Illinois) and S.
Sarkar (Univ. of Oxford). Big-Bang nucleosynthesis (BBN) oﬀers the deepest reliable probe of the early Universe. Primordial or Big Bang Nucleosynthesis (BBN) Gamow, Herman and Alpher also believed that the high temperature of the universe is an appropriate condition for nuclear processes to occur during the first few minutes of Big Bang.
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. One second after the Big Bang, the temperature of the universe was.
Ever since, there have been no serious competitors to the Big Bang, and a plethora of other predictions, such as big-bang nucleosynthesis, the details of structure formation, the presence of pristine gas in the early Universe. The modeling of the early universe by the standard big bang model gives a scenario that involves twelve nuclear interactions that led to the present cosmic abundances of elements outside the stars.
The vast majority of the mass of ordinary matter in the universe is hydrogen and helium, remaining. Big Bang. The universe begins in a sudden mysterious event called the Big Bang.
We don’t know what caused it to happen. Matter created. The energy of the new-born universe creates matter.