This first process, Big Bang nucleosynthesiswas the first type of nucleogenesis to occur in the universe. After 50 years of efforts, researchers have just begun to understand its mechanism. As a main sequence star ages, the core temperature will rise, resulting in a steadily increasing contribution from its CNO cycle.
In the cores of stars, in supernova explosions, and merging neutron stars, new atoms are manufactured from nuclear fusion reactions. The combinations go in this order: Carbon plus helium produces oxygen.
The continuation of this nucleosynthesis process will be made difficult by the high Coulomb barrier that the nuclei have to overcome.
How, where and when was it produced?
More massive stars burn Hydrogen into Helium through a chain of reactions involving Carbon, Nitrogen and Oxygen inherited from previous stars through a process called the CNO cycle. Hartman, K. Farouqi, O.
Without the heat of fusion, the star collapses and explodes in a shockwave. Elements with odd numbers of protons are formed by other fusion pathways.
Yet there is gold on Earth, both in its deep core, where it has migrated together with heavy elements such as lead or silver, and in the planet's crust, which is where we extract this precious metal.