Stars elements heavier than lithium

We have seen in this section, that there occurred a short phase in the early universe when density and temperature was high enough for the fusion of hydrogen into heavier elements up to lithium and boron. Hydrogen (protons) was present since protons were formed form quark particles. Neutral hydrogen since the recombination age. However, the second constiment of water molecules, oxygen, was not formed dming these phases. In the next section we will describe the evolution of stars and see how elements heavier than lithium can be synthesized by thermonuclear fusion reactions inside stars. 

Two dominant themes run throughout the evolution of late type star compositions the abundances of the isotopes of carbon, nitrogen, and oxygen, and the abundances of the metals heavier than the iron peak - the neutron capture elements usually associated with the s-process. In addition to these elements, the abundance of lithium can also be a distinguishing characteristic of some groups, and can be used to interpret possible origins for some of these peculiar stars. 

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