Star of very great natural luminosity and relatively enormous size, typically several magnitudes brighter and several times larger than a giant star. Like other classes of stars, they are distinguished in practice by examination of certain lines in their spectra (see spectroscopy). A supergiant may have a diameter several hundred times that of the Sun and a luminosity nearly a million times as great. Supergiants live probably only a few million years, an extremely short life for a star.
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