Energy production in stars.

where M= 1.99.1033 g is the sun’s mass, R= 6.g6.10’0 cm its radius, and G= 6.6710 the gravitational constant. A similar energy was set free when the sun was assembled from interstellar gas or dust in the dim past; actually somewhat more, because most of the sun’s material is located closer to its center, and therefore has a numerically larger potential energy. One-half of the energy set free is transformed into kinetic energy according to the wellknown virial theorem of mechanics. This will permit us later to estimate the temperature in the sun. The other half of the potential energy is radiated away. We known that at present the sun radiates