Convective zone

The region within a star in which the predominant form of energy movement is by convection, that is, moving currents of fluid from a hot to a cooler region. Vast cells of hot gas become buoyant and rise through their surroundings, carrying energy with them. As they release this energy in the higher, less dense regions of the star, conditions change and the gas cell sinks back down into the deeper interior regions. In the Sun, the convective zone begins just below the photosphere and extends for a distance equivalent to on fifth of a solar radius. In less massive stars than the Sun, the convective zone extends through much more than one fifth of the star's radius. In high mass stars, however, the convective zones are often much smaller and, in some cases, insignificant.