The star cluster R136 in the central region of the Tarantula Nebula.(Image credit: NASA, ESA, and P. Crowther (University of Sheffield)

Blue stars are by far the biggest and brightest stars in the galaxy.

To the naked eye, the stars in the night sky all look very similar to each other, the main difference between them being that some are brighter than others. But if you look more carefully, you’ll see that stars come in different colors.

Most of them look white, but some are distinctly red in color while others are blue. A star’s color tells us about its temperature and mass, and blue stars are the hottest and most massive of all.

Any star that has three or more times as much mass as the sun will tend to look blue to our eyes. That’s irrespective of other factors such as chemical composition; blue stars, yellow stars and red stars alike are made up of around 75% hydrogen, 24% helium and smaller amounts of other elements. But the fact that blue stars are more massive means they generally have higher intrinsic luminosities than other stars. This means they can be a long way away and still remain visible in the sky.