How do AGB stars lose mass?
During a star’s post-main-sequence (MS) evolution, it will lose much of its starting mass through stellar winds. AGB stars have even stronger stellar winds, meaning they are losing mass at an even more rapid rate than RGB stars.
What is the AGB phase of a star?
For stars less massive than about nine times the mass of the sun, the last major phase of life is as an Asymptotic Giant Branch (AGB) star. This final phase of hydrogen burning happens after the star has moved from the Main sequence, through the Red Giant Phase and past the Horizontal Branch (see figure 1).
How does a star evolve within the asymptotic giant branch AGB phase?
During the E-AGB phase, the main source of energy is helium fusion in a shell around a core consisting mostly of carbon and oxygen. During this phase, the star swells up to giant proportions to become a red giant again. The star’s radius may become as large as one astronomical unit (~215 R ☉).
Why do AGB stars pulsate?
The Asymptotic Giant Branch (referred to as AGB) phase is characterized by the occurrence of thermal pulsations. It is well known that this type of pulsation is caused by the thermal runaway caused by helium burning confined in a relatively thin shell surrounding an inactive carbon- oxygen core.
What happens to the shell of gas and dust lost by an AGB star?
The double-shell burning structure of AGB stars, i.e., a He-burning inner shell which is replenished by a H-burning outer shell, leads to a phenomenon called He-shell flash, or thermal pulse.
What is a post AGB star?
Post-AGB stars are luminous objects of low and intermediate initial mass (M* ≤ 8–9 M⊙) in a final stage of evolution: they ended their Asymptotic Giant Branch (AGB) evolution by a phase of very strong mass loss (10−7–10−4 M⊙ yr−1), evolve on a fast track to hotter effective temperatures at roughly constant luminosity …
How long does the AGB phase last?
“AGB” stars are very rare: this phase is very brief and lasts perhaps 105 yr. Later the star becomes a “post-AGB star” and this phase is probably even shorter, perhaps a few times 104 yr; during this phase the object moves towards higher effective temperatures at constant luminosity and will become a planetary nebula.
Will the sun become an AGB?
The Sun, towards the end of its life, will become an Asymptotic Giant Branch (AGB) star. Once exhausted its primary Hydrogen nuclear fuel, it will ultimately become 10,000 times more luminous than it is today, and swell beyond the orbit of our planet. When that will happen, Earth will be engulfed and vaporized.
How long does the AGB last?
AGB stars are long-variable pulsators, with typical pulsation periods of 100-1000 days. During a pulsation cycle the variation in brightness is drastic, up to several orders of magnitude in visual light.
