Institute of Astronomy

Number of stars in a galaxy

Published on 24/06/2013 
Question: 

As an astronomer when you look at distant galaxies do you sometimes wonder what it would be like in those galaxies? Perhaps ellipictal and dwarf galaxies not spiral galaxies because our milky way is one of them. Also how do astronomers approximate the number of stars in each galaxy?

It is indeed interesting to think about what it would be like in a different galaxy, or even in a different part of our own galaxy.  Nearer to the galactic centre for example there would be many more stars in the night sky.

To approximate the number of stars in a galaxy essentially what we do is look at how bright the whole galaxy is and then divide that by the brightness of an individual star.  There are additional things we do to make it more accurate however, not all stars are the same mass and brightness for example, and there may be dust in the galaxy obscuring some of the stars, but we can look at the spectrum of light from the galaxy (how bright it is at different wavelengths) to help us disentangle these problems.

Page last updated: 24 June 2013 at 18:10