Size and Temperature of Stars
The different colours of Orion
Credit: A. Vannini et al.
Stars come in lots of different colours.
The colour depends on the temperature of the star:
- Hot stars are blue.
- Cooler stars are red.
Hot stars can be as hot as 30,000 °C or more, but the coolest stars are only 1,000 °C.
The Sun is quite a cool, yellow star. It is about 6,000 °C.
The temperature of a star, and so its colour, depends on the amount of mass it has.
Very massive stars, tens of times the mass of the Sun, are the hottest, and smaller stars with less than half the mass of the Sun, are the coolest.
Although they are bigger, the hot, blue stars do not "live" as long as the smaller ones because they use up their nuclear fuel much more quickly.
