supergiants is one of the massive and most luminous star that has a visual magnitudes between about −3 and −8, the temperature range from about 3,400 K to over 20,000 K. its element are different from less luminous stars. It shows helium and nitrogen at the surface due to convection of these fusion products to the surface, helium is also formed in the core and shell by fusing hydrogen and nitrogen. They contain carbon-13, lithium and s-process elements and also enriched with oxygen.
It is sex-linked: genetic red-green color blindness affects males much more often than females, because the genes for the red and green color receptors are located on the X chromosome, of which males have only one and females have two.
