The Sun
- The Sun lies at the centre of the Solar System
- The Sun is a star which makes up over 99% of the mass of the solar system
- The fact that most of the mass of the Solar System is concentrated in the Sun is the reason the smaller planets orbit the Sun
- The gravitational pull of the Sun on the planets keeps them in orbit
- The Sun is a medium sized star consisting of mainly hydrogen and helium
- It radiates most of its energy in the infrared, visible and ultraviolet regions of the electromagnetic spectrum
Our Sun (Image courtesy of NASA)
- 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