Stellar Structure

Abstract

THE current argument against Helmholtz's contraction hypothesis concerning the origin of the sun's heat may be summarised as follows. The gravitational potential at a point within the sun is of the order of magnitude of its value at the surface, 2 × 10¹⁵ c.g.s. units. Thus contraction may have supplied energy 2 × 10¹⁵ ergs per gram of the sun's mass. The sun now radiates 1.9 ergs per second for each gram of its mass. Further, the earth's crust has been solid for at least 1.5 × 10⁹ years, during which time the sun may have radiated 9 × 10¹⁶ ergs for each gram of its mass. Hence “it appears that the Helmholtz contraction-hypothesis cannot account for more than about two per cent of the energy which has been radiated by the sun during the earth's life” (Jeans, “Astronomy and Cosmogony”, p. 106). Further, there is astronomical evidence that the whole life of the sun has been at least of the order of 10¹³ years.