The rate at which the energy of a blackbody radiation is converted into neutrinos by the pair annihilation process $e^{-}+e^{+}\to \nu +\overline{\nu }$ has been calculated. At $T\sim 6\times {10}^9°$K the relaxation time for such conversion process is around 100 sec for pure radiation. Since neutrinos have a very long mean free path (≫stellar dimensions) they will escape, thus carrying away the energy. This process therefore will be of astrophysical importance. The rate of energy loss $\frac{\mathrm{dU}}{\mathrm{dt}}$ is tabulated, as a function of temperature and density, together with the chemical potential, the pressure, and the electron-positron energy. This table should be useful for numerical integrations of stellar structure equations in the temperature range (0.5-10)×${10}^9$ °K, and the density range 0-${10}^9$ g/${\mathrm{cm}}^3$.

• Received 31 March 1961

DOI:https://doi.org/10.1103/PhysRev.123.1040