First, the team compiled information about the masses, luminosities, and such for stars of different ages, focusing especially on asymptotic giant branch
Abstract: Planetary Nebulae represent a powerful window into the evolution of low-intermediate mass stars that have undergone extensive mass-loss on the asymptotic giant branch
The conditions are just right in the atmospheres of cool, aged stars--red giants and stars on the asymptotic giant branch
of the Hertzsprung-Russell diagram, which charts the stages of stellar evolution (S&T: March 1999, page 43).
The responsible party is a so-called asymptotic giant branch
star, which powers itself by two fusion reactions.
Such a star is called an asymptotic giant branch
(AGB) star, thanks to the shape of its evolutionary track on the Hertzsprung-Russell diagram (see page 39).
We followed the Sun as it became a red giant (undergoing considerable mass loss); as it encountered a violent helium core flash; as it underwent quiescent helium burning in its core; as it became a red giant for the second time while traversing the asymptotic giant branch
(AGB) |on the Hertzsprung-Russell diagram~, where it encountered violent repetitive helium shell flashes and again suffered considerable mass loss; and as it left the AGB .