The Sun has evolved over a period of some 4.7 × 109 years. Standard theory tells us that the luminosity has smoothly risen from an initial level only 70% the current value. Recent ideas suggest a scenario in which the luminosity was never far below current levels, but this remains highly speculative. Stellar structure and evolution theory has been quite successful in describing general properties of the Sun and stars, but conflicts with observation do remain. We currently lack an adequate theory of the solar cycle. Several physical mechanisms have been proposed that could lead to luminosity variations on many time scales.
All Science Journal Classification (ASJC) codes
- Ecology, Evolution, Behavior and Systematics
- Earth-Surface Processes