Colours of Stars

Constellation of Orion
Credit: Rogelio Bernal Andreo

Stars shine in lots of different colours. Their colour tells us the temperature of the star.

Some stars shine with a red-ish colour. This means they are quite cool for stars - only 3000 °C or less. Other stars shine with blue-ish glow. This means they are much hotter -over 30,000 °C! The Sun is shines with a yellow-ish colour and is about 6,000 °C. This makes the Sun a relatively cool star. 

The temperature of a star depends on how much mass it has. Very massive stars, which can be over ten times the mass of the Sun, are the hottest and usually glow blue. Smaller stars, with less than half the mass of the Sun, are the coolest and usually glow red.

The more massive, hotter blue stars do not "live" for as long as the smaller stars. This is because they use up fuel through nuclear fusion much more quickly. The hottest stars only shine for a few million years. However, the smallest stars will shine for hundreds of billions of years. As an average sized star, our Sun is about halfway through its 10 billion year lifetime.