The explosive event that occurs when helium burning begins in the core of a low-mass star. The core must be dense enough for degeneracy effects to be important. A degenerate gas does not expand on heating, and is unable to cool through expansion in the way that a non-degenerate gas would. Thus, as helium begins to burn, the temperature rises rapidly, eventually becoming so high that the gas is no longer degenerate. At this point the core expands very rapidly, releasing its stored energy in less than 2 min.