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Supergiant (or supergiant star) is a term generally used for a very bright giant star. Such stars are post-main-sequence stars that were massive and hot during their main-sequence, e.g., O-type stars. The term generally means brighter than a bright giant. The very brightest supergiants are termed hypergiants. The term supergiant is not consistently defined, but is applied to stars in this general range:
-3 to -8 | absolute magnitude |
1000-1000000 × solar | luminosity |
30-1000 × solar or 0.1-5 AU | radius |
8-12 × solar | mass |
3500-20000 K | temperature |
Since brightness is the criteria, the radii can overlap with "non-super giant" stars. Qualifications used for some of the brightest:
Supergiants can be of various spectral classes and can be red, blue, or yellow. Examples of supergiants:
Blue supergiant characteristics:
10000-1000000 × solar | luminosity |
10000-50000 K | temperature |
They are post-main-sequence OB stars.
An extreme helium star (EHe) is a rare type of supergiant nearly devoid of hydrogen. Their formation is a topic of research interest.