Investigate the types of nucleosynthesis reactions involved in Main Sequence and Post-Main Sequence stars

Investigate the types of nucleosynthesis reactions involved in Main Sequence and Post-Main Sequence stars

Proton-Proton chain

Proton-Proton-chain

Proton-Proton-chain-2

Step 3, which produces He-2, depends on the temperature of the star

  • For temperature between 10-14 MK , helium-4 is produced by fusing two helium-3 nuclei.
  • For temperature between 14 – 23 MK and exceeding 23 MK, 3He fuse with pre-existing 4He to form beryllium-7, which undergoes further reactions to produce two helium-4 nuclei.

– CNO (carbonnitrogenoxygen) cycle

CNO cycle: common in larger stars – uses C as a catalyst and requires hotter temperatures

CNO-cycle

CNO-cycle-2
 
Extract from Physics Stage 6 Syllabus © 2017 NSW Education Standards Authority (NESA)