Since the universe is presumed to be homogeneousit has one unique value of the baryon-to-photon ratio. Further support comes from the consistency of the other light element abundances for one particular baryon density and an independent measurement of the baryon density from the anisotropies in the cosmic microwave background radiation.
The major types of nucleosynthesis[ edit ] Big Bang nucleosynthesis[ edit ] Main article: The present measurement of helium-4 indicates good agreement, and yet better agreement for helium Lithium Lithium-7 and lithium-6 produced in the Big Bang are in the order of: 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.
Therefore, the current abundance of the elements must be explained by any model of what happened in the early universe. In the 's and 60's the predominant theory regarding the formation of the chemical elements in the Universe was due to the work of G.
The discrepancy is a factor of 2. Those abundances, when plotted on a graph as a function of atomic number, have a jagged sawtooth structure that varies by factors up to ten million. These should not be confused with non-standard cosmology: It seems like we really understand the physical processes which went on in the first few minutes of the evolution of the Universe!
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.
More recently, the question has changed: If conditions had been different, we wouldn't have wound up with that ratio. Hydrogen and helium are most common, residuals within the paradigm of the Big Bang. It would also be necessary for the deuterium to be swept away before it reoccurs.
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Further details can be found here. Furthermore, one value of this baryon density can explain all the abundances at once.
As noted above, in the standard picture of BBN, all of the light element abundances depend on the amount of ordinary matter baryons relative to radiation photons. 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.
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. Also, we know that most of the hydrogen in the universe is in the form of simple hydrogen, not its heavier isotopes deuterium or tritium.
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.
Hoyle's work explained how the abundances of the elements increased with time as the galaxy aged. March Learn how and when to remove this template message Deuterium is in some ways the opposite of helium-4, in that while helium-4 is very stable and difficult to destroy, deuterium is only marginally stable and easy to destroy.
This is one of the corner-stones of the Hot Big Bang model. 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.
One can insert a hypothetical particle such as a massive neutrino and see what has to happen before BBN predicts abundances that are very different from observations.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. Helium is the second most abundant element in the visible universe and its cosmological significance was recognised by Alpher et al.
(), although a realistic theory of its abundance from primordial nucleosynthesis, depending primarily on the neutron–proton ratio and hence the temperature at the epoch of charged-current weak-interaction. Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons.
Little of the atmospheric argon is primordial. Helium-4 is produced by alpha-decay, and the helium trapped in Earth's crust is also mostly non-primordial. Nucleosynthesis is the process by which chemical elements and their isotopes are formed.
The heavy elements (carbon and heavier ones) are thought to be the result of thermonuclear burning in stars, and especially the relatively rare stars that become supernovae. Big Bang nucleosynthesis generated few elements: only hydrogen, deuterium, some of the helium and lithium, traces (if any) of.
Big Bang nucleosynthesis generated few elements: only hydrogen, deuterium, some of the helium and lithium, traces (if any) of beryllium and boron. After a brief overview of the physical processes involved therein, we present the predictions of the primordial nucleosynthesis in the standard Big Bang model and compare them to the .Download