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
|8-12 × solar||mass|
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|
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.