Classification of Stars
- Stars come in a wide range of sizes and colours, from yellow stars to red dwarfs, from blue giants to red supergiants
- These can be classified according to their colour
- Warm objects emit infrared and extremely hot objects emit visible light as well
- Therefore, the colour they emit depends on how hot they are
- A star's colour is related to its surface temperature
- A red star is the coolest (at around 3000 K)
- A blue star is the hottest (at around 30 000 K)
The colour of a star correlates to its temperature
- This is why white dwarfs, for example, are very hotĀ and red giants are red because they are cool
- Astronomical objects cool as they expand and heat up as they contract, such as when a star reaches the end of its life and becomes a red giant
- This means that their colour will also change accordingly with their temperature
Exam Tip
We often remember red as being hot and blue as cool in everyday life, but remember this is the other way around when describing the temperature of stars!
