Later Phases

Abstract

The stellar evolution described above may seem to be rather complicated, at least where the changes of the surface layers are concerned, for example, in the case of evolutionary tracks in the HR diagram. The processes appear much simpler and even become qualitatively predictable if we concentrate only on the central evolution. Extrapolating from central hydrogen and helium burning of sufficiently massive stars, we can imagine that the central region continues to pass through cycles of nuclear evolution which are represented by the following simple scheme: The momentary burning will gradually consume all nuclei inside the convective core that serve as “fuel”. The exhausted core then contracts. This raises the central temperature until the next higher burning is ignited etc.