Abundance of lighter elements and nucleosynthesis

how much of the universes ordinary matter is thought to be helium

While the helium-3 content can only be determined with substantial uncertainty, the results appear to be the same for all regions, whatever their distance to the galactic center. As the universe cooled, the neutrons either decayed into protons and electrons or combined with protons to make deuterium an isotope of hydrogen.

Abundance of lighter elements and nucleosynthesis

The two general trends in the remaining stellar-produced elements are: 1 an alternation of abundance of elements according to whether they have even or odd atomic numbers, and 2 a general decrease in abundance, as elements become heavier.

In search of primordial helium, one selects among the dwarf galaxies those that are especially poor in oxygen and nitrogen.

Where do elements come from

Paresce, F. This is in very good agreement with observations and is another major triumph for the Big Bang theory. The discrepancy is a factor of 2. Fowler , Alastair G. And what is that strange dip in the Li abundance? Lemke, D. These pieces of additional physics include relaxing or removing the assumption of homogeneity, or inserting new particles such as massive neutrinos. Their constant lithium content has, in fact, given these stars their name: They are called lithium-plateau stars or, alternatively, Spite plateau stars after the plateau's discoverers. As both the predictions and the analyses of observations are bound to improve over time, some changes are to be expected. History of nucleosynthesis theory[ edit ] The first ideas on nucleosynthesis were simply that the chemical elements were created at the beginning of the universe, but no rational physical scenario for this could be identified. A point's horizontal position indicates the abundance of oxygen, its vertical position the abundance of helium

During the s, there were major efforts to find processes that could produce deuterium, but those revealed ways of producing isotopes other than deuterium. For a long time, this meant that to test BBN theory against observations one had to ask: can all of the light element observations be explained with a single value of the baryon-to-photon ratio?

If such a cloud is sufficiently hot, certain atomic reactions involving helium atoms more precisely, helium atoms regaining an electron they had previously lost lead to characteristic emissions of electromagnetic radiation at precisely defined frequencies.

cosmic microwave background radiation

Unsourced material may be challenged and removed. Thuan University of Virginia ] Judging by the oxygen and nitrogen they contain, dwarf galaxies are comparatively primitive.

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Big Bang Nucleosynthesis