Physical Assumptions of the
Standard Solar Model

The Standard Solar Model is based on the following physical assumptions:

1. The Sun was formed from a homogeneous mixture of gases.

2. The Sun is powered by nuclear reactions in its core.
3. The Sun is a body in hydrostatic equilibrium, with the gravitational forces that are attempting to compress it exactly balanced by gas and radiation pressure generated internally.
4. Energy is transported from the core of the Sun, where it is produced, to the surface, where it is radiated into space, by photons (radiative transport) and by large-scale vertical motion of packets of hot gas (convection).

Standard Solar Model

The Sun is by far the most studied star. We have a large amount of data, and considerable understanding of how the Sun functions. This has allowed astronomers to construct the Standard Solar Model: a mathematical model of the Sun that uses a basic understanding of such fields as nuclear and atomic physics, measured key quantities, and a few assumptions to describe all solar observations. Since we believe the Sun to be a representative star, the Standard Model by implication is expected to be a reasonable starting point for understanding the structure of other stars also.

The essential general assumptions of the Standard Solar Model are summarized in the adjacent box. It uses as input our best physical theories of these processes and measured parameters such as the rates for critical nuclear reactions and the solar energy output.