helium shell flash

helium shell flash

A violent outburst of energy that occurs periodically in a highly evolved giant star. The star is producing energy in a shell of hydrogen and in an inner shell of helium surrounding the inert dense core of carbon and oxygen. Helium shell burning is unstable, producing energy mainly in short intense flashes. After a shell flash, which causes the star to expand then cool, the convective region in the outer part of the star goes deeper and may dredge up carbon to the surface.
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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 .