A star that occupies a strip in the Hertzsprung–Russell diagram that is almost parallel to, and just above, the giant branch. Stars evolve from the horizontal branch to the asymptotic giant branch when they have exhausted the helium in their core and are burning it in a shell (see Helium Shell Flash). At the end of the AGB stage, stars with between about 1 and 8 solar masses undergo extensive mass loss through a vigorous stellar wind, exposing the core and leaving the star with a surrounding envelope of gas and dust. A star in such a stage is known as a post-AGB star, or a protoplanetary nebula.
Subjects: Astronomy and Astrophysics.