A star’s colour tells us a lot about the nature of the star itself. Small red dwarfs and massive red supergiants are extremely different types of stars but have one thing in common – they have a similar surface temperature, albeit very different radii and eventual fates!

However, observers of the night sky will soon notice that stars sometimes appear to twinkle and shimmer, appearing even to drastically change colour.

This is, however, not due to the star itself drastically changing its surface temperature and thus its colour.

The phenomenon arises due to scintillation in the earth’s atmosphere – as the incoming light passes through our atmosphere, it is refracted by the constituent gases in our atmosphere, resulting different colours being refracted in different directions over a short period of time.

With particularly strong scintillation, to an observer on the earth’s surface, the star thus appears to be changing colour!