Defining Nucleosynthesis
Nucleosynthesis is the process by which new atomic nuclei are created from pre-existing nucleons (protons and neutrons) or other nuclei. It is the fundamental cosmic mechanism responsible for the formation of all chemical elements observed in the universe, explaining their relative abundances.
Main Types of Nucleosynthesis
There are several key types of nucleosynthesis, primarily categorized by where and when they occur. The earliest form is Big Bang Nucleosynthesis (BBN), which created light elements in the early universe. Later, Stellar Nucleosynthesis forged heavier elements inside stars, and Supernova Nucleosynthesis is responsible for the heaviest elements during stellar explosions.
Big Bang Nucleosynthesis (BBN) Example
During the first few minutes after the Big Bang, the universe was hot and dense enough for protons and neutrons to fuse. This early nucleosynthesis produced most of the universe's helium, along with traces of lithium and deuterium (heavy hydrogen), but no heavier elements could form due to rapidly decreasing temperature and density.
Stellar Nucleosynthesis and Element Formation
Stars act as cosmic furnaces, undergoing stellar nucleosynthesis throughout their lives. Through nuclear fusion in their cores, stars convert hydrogen into helium, then helium into carbon, oxygen, and progressively heavier elements up to iron. These elements are then dispersed into space through stellar winds or supernova explosions, enriching the interstellar medium for future star and planet formation.