Elements heavier than iron may be made in neutron star mergers or supernovae after the r-process. These processes are able to create elements up to and including iron and nickel.
The distance a photon can travel before hitting a matter particle is called the mean free path.
Using this value, are the BBN predictions for the abundances of light elements in agreement with the observations? The seminal review paper by E.
Hoyle proposed that hydrogen is continuously created in the universe from vacuum and energy, without need for universal beginning. A very influential stimulus to nucleosynthesis research was an abundance table created by Hans Suess and Harold Urey that was based on the unfractionated abundances of the non-volatile elements found within unevolved meteorites.
The abundance ratio was about seven protons for every neutron. Neutron capture can happen by two methods, the s and r-processes, where s and r stand for slow and rapid.
Radiation, in the form of photons, and matter, in the form of protons, neutrons and electron, can interact by the process of scattering. At the same time it was clear that oxygen and carbon were the next two most common elements, and also that there was a general trend toward high abundance of the light elements, especially those composed of whole numbers of helium-4 nuclei.
Almost all the hydrogen and helium present in the universe today and some of the lithium were created in the first three minutes after the big bang.
However, much of the Universe is in the form of dark matter, which brings the value of M to 0. Some boron may have been formed at this time, but the process stopped before significant carbon could be formed, as this element requires a far higher product of helium density and time than were present in the short nucleosynthesis period of the Big Bang.
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