The Formation of Stars by the Condensation of diffuse Matter

Zusammenfassung

Stars are not static systems in a permanent state of equilibrium. This fact was recognized even in the days of Kelvin and of Helmholtz, who were, perhaps, the first scientists to ask themselves what power it is that keeps the Sun (and the stars) shining. In the nineteenth century, nuclear power, and Einstein’S relation between mass and energy, were unknown. Gravitational effects provided the most potent source of energy which could be envisaged. The attempt was made to estimate the age of the Sun on the basis of its present luminosity and its present gravitational self-energy. As is well known the resulting time-scale was of the order of 5 × 10⁷years : even in those days there was geological and paleontological evidence that the age of the Earth itself was far greater than this.