What are the characteristics of a supergiant star?
Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars spans from about 3,450 K to over 20,000 K.
What are some examples of red and blue supergiants?
Some great examples of red supergiants are Antares, Betelgeuse, and Mu Cephei. Blue supergiants are just as rare as red supergiants, and their spectral type is usually O, B. Blue supergiants are the hottest stars in the universe, having temperatures of around 10,000 K to 50,000 K or more.
What is a post-red supergiant star?
Post-red supergiant stars have a higher level of nitrogen relative to carbon due to convection of CNO-processed material to the surface and the complete loss of the outer layers. Red supergiants have a prevalence of around 0.001% and are of spectral type K, and M.
What is the difference between K type stars and red supergiants?
The K-type stars, especially early or hotter K types, are sometimes described as orange supergiants (e.g. Zeta Cephei ), or even as yellow (e.g. yellow hypergiant HR 5171 Aa). Red supergiants are cool and large. They have spectral types of K and M, hence surface temperatures below 4,100 K.
What is the luminosity of a blue hypergiant star?
Because yellow hypergiants are post-red supergiant stars, there is a fairly hard upper limit to their luminosity at around 500,000–750,000 L☉, but blue hypergiants can be much more luminous, sometimes several million L☉.
Where do supergiant stars lie on the HR diagram?
Supergiant stars lie around the horizontal band occupying the entire upper portion of the HR diagram, however, there are some variations at different spectral types. These variations are partly due to different methods for assigning luminosity classes at different spectral types, and partly to actual physical differences in stars.