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

> Edexcel GCSE Physics (1PH0) — 7.1 Astronomy (Phys only) · Describe · 4 marks

## Mark scheme (4 marks)

1. A nebula (cloud of dust and gas) is pulled together by gravitational attraction to form a protostar
2. The protostar becomes a main sequence star where gravitational forces and outward pressure (from fusion) are balanced
3. When hydrogen runs out, the star expands to form a red giant (where heavier nuclei are produced by fusion)
4. Once fusion reactions end, the star contracts and cools to form a white dwarf

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Physics (1PH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-life-cycle-of-a-930142f2) · Published by Druglandscape Ltd.