|Compare supergiant Sometimes shortened to: giant any of a class of stars, such as Capella and Arcturus, that have swelled and brightened considerably as they approach the end of their life, their energy supply having changed|
A very large, bright non-main-sequence star that burns hydrogen at a much faster rate than a dwarf star. Giant stars are much more luminous and have shorter lifespans than the slower-burning dwarfs. The larger the giant, the shorter its lifespan; the largest stars, with solar mass of around 100, blaze at several hundred thousand times the energy of the Sun and will last only a few million years, a very brief time when compared with the Sun's 10-billion-year lifespan. Giant stars usually end their lives as supernovae , but even before that event the immense ultraviolet radiation they produce has a dramatic impact on their stellar surroundings; the presence of a giant star in a star system prevents the formation of new protostars because the radiation from the giant star breaks apart any nearby nebulae.