# Explain how the colour of a star can be used to determine its surface temperature, and describe how the light from distant stars provides evidence that the universe is expanding.

> Eduqas A-Level Physics — 6.3 Stellar evolution and cosmology (A-Level only) · Explain · 5 marks

> Stars emit electromagnetic radiation across a range of frequencies. Astronomers study this radiation to learn about the properties of stars and the universe.

## Mark scheme (5 marks)

1. Stars behave as black bodies, absorbing and emitting radiation across a range of frequencies.
2. Hotter stars emit radiation at higher peak frequencies, so they appear blue/white; cooler stars emit at lower peak frequencies, so they appear red/orange.
3. The light from distant galaxies/stars is shifted towards the red end of the electromagnetic spectrum (redshift).
4. This redshift indicates that stars and galaxies are moving away from us / that the universe is expanding.
5. The further away a galaxy is, the greater its redshift, showing it is moving away faster, which supports the idea that the universe began from a single point (Big Bang).

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-colour-of-a-792a71cb) · Published by Druglandscape Ltd.