Nucleosynthesis Of Light Elements

The predictions of the element abundances in the "standard", hot, big bang cosmological model (SBBN) are described.

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The more oxygen and nitrogen a region of space contains, the more its light element abundances are bound to have been influenced by stellar nuclear fusion.

The most direct - and thus most solid - prediction of Big Bang Nucleosynthesis concerns helium-4, each nucleus of which consists of two protons and two neutrons.

All carbon-based life on Earth is literally composed of stardust.

In 1948, Physicist George Gamow hypothesized that all of the elements might have been made in the hot and dense early universe.

Alpher and Herman found that Gamow was wrong: most elements could not have been made in the early universe. Neutrons decay in about 10 minutes, and their density decreases as the universe expands in that time.

There just isn't enough time to keep building up to the heavier elements before the neutrons are gone. Only the lightest elements are built up in the early universe.

Fortunately for astronomers, there are indicators of how much chemical evolution particular objects have undergone, most importantly the presence of elements such as oxygen and nitrogen.

These are elements with nuclei that are produced by nuclear fusion reactions in stars, but that definitely could not have been produced during Big Bang Nucleosynthesis.

A brief overview can be found in the spotlight text Big Bang Nucleosynthesis: Cooking up the first light elements.

This text, in contrast, is concerned with the crucial question: If we want to test these predictions, how do we determine the original ("primordial") abundances of the different light nuclei?