# Explain the life cycle of a star that is similar in size to the Sun, starting from a nebula and ending at its final state.

> Edexcel A-Level Physics (9PH0) — 7.3 Magnetic fields and electromagnetic induction · Explain · 5 marks

## Mark scheme (5 marks)

1. A nebula (cloud of dust and gas) is pulled together by gravitational attraction to form a protostar
2. The protostar becomes hot enough for hydrogen nuclei to undergo fusion, forming a main sequence star where gravitational forces and outward pressure are balanced
3. When hydrogen is used up, the star expands to form a red giant, where heavier nuclei are produced by fusion
4. Once all fusion reactions are complete, the star contracts under gravity
5. The star cools down to form a white dwarf as its final state

## Key terms

- [nebula](https://www.gradenine.co.uk/glossary/nebula)

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-the-life-cycle-of-a-5bea5757) · Published by Druglandscape Ltd.