The Deep Interiors of Stars

Abstract

With what we now know about the luminosities, radii, masses, and chemical compositions of stars like the sun, our investigation of their internal structures will reveal to us the conditions that must hold throughout a star’s interior if its luminosity is to be consistent with its known mass and radius. To guide us in this investigation we introduce two general principles that ensure the dynamical and thermal stability of a star. The first of these imposes the condition of dynamical equilibrium at each point within the star. This means that the star is neither exploding nor collapsing, nor even, for that matter, pulsating. It does not mean, however, that the material within a star is at rest; it means that there is no outward or inward accelerated motion, nor any net outward or inward flow of material at any point. It is permissible under this condition to have a slow circulation of material (convection currents) in various zones of the star.

He passed the flaming bounds of space and time:

The living throne, the sapphire-blaze,

Where angels tremble while they gaze,

He saw; but blasted with excess of light,

Closed his eyes in endless night.

—THOMAS GRAY, The Progress of Poesy