Stellar Nucleosynthesis | 20 May 2024

Source: TH

Stellar nucleosynthesis is the process by which stars create the elements inside their cores. The only element not formed in this way is hydrogen, the most abundant and lightest element in the universe.

• Stellar cores have crushing pressures and temperatures, reaching up to 15 million °C in the Sun's core. In these harsh conditions, the nuclei of atoms undergo nuclear fusion.
  • The hydrogen nucleus, which is just one proton, comes together to form helium nuclei (two protons and two neutrons) in the p-p (proton-proton) process.
  • In more massive stars, the carbon-nitrogen-oxygen (CNO) cycle dominates, where the nuclei of these elements come together in different ways to form elements from helium onwards.
    • CNO cycle involves hydrogen fusing into helium, catalysed by carbon, nitrogen, and oxygen isotopes.
  • As a star runs out of nuclei to fuse, its core contracts, increasing the temperature and triggering further nuclear fusion.
  • This process continues until the star starts producing iron, the lightest element for which fusion consumes more energy than it releases.
    • Elements heavier than iron can only be synthesised outside a star when it goes supernova.

Read More: Nuclear Fusion Energy