Red giant and the creation of a planetary nebula finally ends the red-giant phase of the star's evolution. The red-giant phase typically lasts only around a billion years in total for a solar mass star, almost all of which is spent on the red-giant branch. The horizontal-branch and asymptotic-giant-branch phases proceed tens of times faster. If the star has about 0.2 to , it is massive enough to become a red giant but does not have enough mass to initiate the fusion of helium. These "intermediate" stars cool somewhat and increase their luminosity but never achieve the tip of the red-giant branch
Giant star of distinct evolutionary phases of their lives: a main red-giant branch (RGB); a red horizontal branch or red clump; the asymptotic giant branch (AGB), although AGB stars are often large enough and luminous enough to get classified as supergiants; and sometimes other large cool stars such as immediate post-AGB stars. The RGB stars are by far the most common type of giant star due to their moderate mass, relatively long stable lives, and luminosity. They are the most obvious grouping of stars after the main sequence on most HR diagrams, although white dwarfs are more numerous but far less luminous.