Nucleosynthesis

Nucleosynthesis periodic table

SolarSystemAbundances

Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons. The first nuclei were formed about three minutes after the Big Bang, through a process called Big Bang nucleosynthesis, which produced hydrogen, helium, and small amounts of lithium and beryllium. In the stars, nucleosynthesis continues to build elements heavier than hydrogen and helium, through processes such as stellar nucleosynthesis, supernova nucleosynthesis, and neutron star merger nucleosynthesis.

Big Bang Nucleosynthesis

Big Bang nucleosynthesis occurred within the first 20 minutes of the universe's existence and is responsible for forming most of the universe's helium, along with deuterium and traces of lithium and beryllium. This process essentially ceased after about 20 minutes, due to the rapid expansion and cooling of the universe.

Stellar Nucleosynthesis

Stellar nucleosynthesis describes the nuclear reactions taking place in the cores of stars to build the elements heavier than hydrogen and helium. This process starts with the fusion of hydrogen into helium in a series of steps known as the proton-proton chain reaction or the CNO cycle (carbon-nitrogen-oxygen cycle). As stars evolve, they can fuse heavier elements in processes like the triple-alpha process (helium burning), which creates carbon, and the carbon burning process, which creates elements up to iron.

Supernova Nucleosynthesis

Supernova nucleosynthesis is a theory of the production of many different chemical elements in supernova explosions, resulting from the nucleosynthesis of elements during the explosion of a massive star. This process is responsible for the creation of elements heavier than iron, which cannot be formed through the fusion processes in stars due to their endothermic nature. Elements such as gold and uranium are thought to be formed in these explosive environments.

Neutron Star Merger Nucleosynthesis

Recent observations and theoretical work suggest that neutron star merger nucleosynthesis is a key site for the production of heavy elements, including those beyond iron that are not formed through supernova nucleosynthesis. During these events, neutron-rich material is ejected into space, where it undergoes rapid neutron capture processes (r-process), leading to the formation of heavy and unstable nuclei that decay into stable forms.

Importance of Nucleosynthesis

Nucleosynthesis has profound implications for understanding the chemical composition of the universe and the distribution of elements across stars, galaxies, and the interstellar medium. It provides critical insights into the life cycles of stars, the history of the universe, and the origins of elements that are essential for life.

See Also

• Stellar evolution
• Galaxy formation and evolution
• Cosmology
• Astrophysics