• noun an extremely large brilliant star that has a luminosity thousands of times greater than that of the Sun
  • Type of very large red giant star at the top right-hand corner of the Hertzsprung-Russell diagram. Betelgeuse in Orion is the most conspicuous example. Supergiants (also red supergiants) are among the brightest of stars, with absolute magnitudes many times greater than those of main sequence stars like the Sun.

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