The growth of helium-burning cores

Helium burning in the convective cores of horizontal branch and red clump stars appears to involve a process of “ingestion” of unburnt helium into the core, the physics of which has not been clearly identified yet. I show here that a limiting factor controlling the growth is the buoyancy of helium entering the denser C+O core. It yields a growth rate that scales directly with the convective luminosity of the core and agrees with constraints on core size from current asteroseismology.