Asymptotic Giant Branch (AGB) Star
An asymptotic giant branch (AGB) star is a low or intermediate mass star (of mass M<8 M⊙) at a late evolutionary phase in its life, during which it appears as a red giant in the Hertzsprung–Russell diagram. After the star has exhausted the supply of He for fusion in its core, it draws energy from He fusion in a shell around the inert carbon-oxygen core, in the early AGB (E-AGB) phase. Later, the star enters the thermally pulsing (TP-AGB) phase, with intermittent burning (fusion) of the hydrogen and He-shells. The thermal pulses occur in timescales of 104–105 years. They mix material from the burning shells to the convective envelope (the 3d dredge-up) and they also induce heavy mass loss from the star (more than 50% of its mass), creating a Planetary Nebula.