ABSTRACT
Most of the energy produced in the nuclear reactions is in the form of photons, which are immediately absorbed in the stellar matter. Their en ergy adds to the thermal reservoir of the star. This energy is responsible for the formation of the pressure gradient needed to support the star against gravity and for the radiation of stellar luminosity. The energy carried by the neutrinos radiates into the interstellar medium directly from the point where it formed; it is not involved in the energy balance of the star and is not included in the observed stellar luminosity. Ordinarily, when we cal culate the energy balance in stars, we subtract the energy carried by the neutrinos directly from the amount of energy produced by nuclear reac tions.
