Why are the stars different colours and why do they change colours?

Did you know that stars are not actually white as they appear to be?

As we all know if you look at the stars on a normal night they will appear to be white. But if you look at them from the dark skies for any amount of time, you will see that they are a diverse variety of colours such as red, yellow, white and blue.

Why is this? Why are the stars not just white?

It turns out that the answer is that the stars are hot. Each star burns at different temperatures. The cooler stars are red (cool still being thousands of degrees!), then hotter ones are sort of yellow hot, and hotter is white hot, with the hottest being bluish.

Why do stars change colour?

So, stars are different colors due to temperture. But why do they change colours still? When you see a red star in the sky, it is likely an old, expanded, dying star. The stable red stars (the ones that are fusing very slowly) are all too small and dim to see without a telescope. The blue stars that you see are the ones that are normally still fusing hydrogen, but are very massive and very hot. A few massive dying stars will turn more blue during some of the later stages of their deaths, and they also make up some of the blue or white stars that you see, but very few.