SUPERGIANT STARS

The brightest stars in the galaxy live fast and die young

Astronomers classify stars according to two main parameters: their intrinsic luminosity and their colour. In these terms, a supergiant is simply any star that lies at the upper end of the luminosity range. But there’s actually quite a difference between blue and red supergiants. A blue supergiant is a comparatively young star that’s so incredibly massive that it burns through all its hydrogen – and hence exits the main sequence – after just a few million years. On the other hand, a red supergiant is a star of somewhat lower mass, though still more than ten times that of our own Sun, that is nearing the end of its life. After passing through the red giant phase of its evolution, it begins a final phase of carbon-forming nuclear fusion, causing it to expand to truly enormous dimensions.