The Life Cycle of a Star

This lesson covers the life cycle of a star, from its formation in a nebula to its eventual death, as required by the AQA GCSE Physics specification (4.8.1). This is a Physics-only topic. You need to understand the different stages a star goes through, how the life cycle depends on the mass of the star, and how heavier elements are formed during the life and death of stars.

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Star Formation — The Nebula

All stars begin life in a nebula — a vast cloud of hydrogen gas and dust in space. A nebula can be many light-years across.

The process of star formation:

1. Gravitational attraction causes the gas and dust in the nebula to clump together.
2. As the material collapses inward, it forms a dense, spinning region called a protostar.
3. The temperature and pressure at the centre of the protostar increase as gravity compresses the material.
4. When the core temperature reaches approximately 15 million degrees C, nuclear fusion begins — hydrogen nuclei fuse to form helium nuclei, releasing enormous amounts of energy.
5. The protostar becomes a main sequence star.