What Role Does Nuclear Fusion Play in the Lifecycle of Stars?

Nuclear fusion is central to the stellar lifecycle. In the main sequence phase, stars fuse hydrogen into helium, balancing the outward pressure from fusion reactions with the inward pull of gravity. As stars exhaust their hydrogen fuel, they enter the red giant or supergiant phase, where heavier elements like carbon, oxygen, and silicon are fused in successive stages. The final stages of fusion can lead to supernova explosions in massive stars, dispersing elements into the interstellar medium and giving rise to new star formation.