Radiation is an important process in main-sequence stars . Convection is the process of transferring energy by motion. We previously discussed convection with respect to granulation on the surface of the sun. It is similar to boiling of water on the stove. Convection happens when the opacity, or the resistance to the flow of radiation, becomes high, as it should in the outer layers of the sun where the temperature is lower than in the core, and some atoms become are no longer ionized and can absorb and re-emit photons.
Convection is also an important process in main-sequence stars .
Before going on to applying what we have learned about how stars operate, let s review what we have learned. It may be a good idea to refer to the star flow chart presented in the last lecture. Hydrostatic equilibrium , or the balance between weight and gas pressure, is the mechanism that keeps a star from dissipating into space, or completely collapsing. Because the weight at the core of the star is very high, the pressure must be high as well. Under conditions of high temperature and density, fusion will take place.