The Lifecycle of Stars

This lesson covers the complete lifecycle of stars from birth to death — as required by the Edexcel GCSE Physics specification (1PH0), Topic 7: Astronomy. This is a Paper 2 topic. You need to know the stages in a star's life, how the path depends on the star's mass, and the role of nuclear fusion and the balance of forces.

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How Stars Are Born

All stars begin their lives in the same way:

Stage 1: Nebula

A nebula is a huge cloud of dust and gas (mainly hydrogen) in space. Nebulae are often referred to as "stellar nurseries" because they are the birthplaces of stars.

Stage 2: Protostar

Over millions of years, gravity causes the dust and gas in a nebula to collapse inward. As the material is compressed, it heats up. This collapsing cloud of hot gas is called a protostar.

• The protostar is not yet a true star — nuclear fusion has not started.
• As more material falls inward, the temperature and pressure at the centre continue to increase.

Stage 3: Main Sequence Star