A giant star with a surface temperature between 2000-3000 Kelvin and diameter 10-100 times greater than the Sun. Red giants are believed to be one of the final phases in the evolution of a normal star, reached only when its central hydrogen has been used up. The star resorts to burning hydrogen in a shell around its dense inert helium core, which results in a rapid inflation of the outer layers of atmosphere. Since red giants are so distended, gravity has only a small effect on the surface layers and many loose considerable amounts of mass into space in the form of stellar winds.