Metal Poor Stars and the Light Element Primary Process - Literature review Example

This paper describes the major nucleosynthesis processes leading to the chemical evolution and formation of stable isotopes of elements, including the neutron-capture features. Among neutron-capture factors created by s- and r-processes, the light neutron-capture elements have been a subject of intense study due to the involvement of a weak r-process which is understood to be one of the processes of their formation. In this paper, an attempt has been made to identify the processes leading to the construction of the various stable isotopes and substantiate the conclusions by using the data from the SAGA database in the context of Light Element Primary Process (LEPP) on which several studies have already been carried out from observatories around the world.

The universe came into existence with a Big Bang followed immediately by a rapid expansion. Before the Bing Bang, the matter was in the form of elementary particles in the quark-gluon-plasma phase consisting of free quarks, leptons and photons (Hempel2010, p7). When the Universe reached the quantum chromodynamics (QCD) phase after elapse of 10-5 s from the Bing Bang at a temperature of around 190 MeV temperature, the quarks became hadrons in the form of baryons and mesons. After the passage of time of 1s, the temperature dropped to 1MeV, resulting in decay of mesons.

The universe was, at that point of time, constituted of protons, neutrons, positrons, electrons and photons. Neutrons decay to form protons if nothing interfered, but protons reacted with neutrons to form heavier He nuclei (Rydberg,2009,5). The baryonic part of the universe evolved from then onwards through nuclear reactions which first began deuterons and then alpha particles.Within three minutes of the Big Bang, the primordial nucleosynthesis was completed, resulting in a matter which consisted of around 76% protons and 24% alpha particles along with traces of 3He, D and 7Li.

The Big Bang Nucleosynthesis (BBN) was completed within 17 minutes. Two other stable isotopes, namely, 4He and 6Li, were produced by the BBN, besides the unstable isotopes tritium or3H,7Be and  8Be(Karki, 2010,p1).