Astronomy 1011A/B Study Guide - Final Guide: Ellipse, Cosmic Calendar, Hyperbola

• School: Western University
• Department: Astronomy
• Course: Astronomy 1011A/B
• Professor: Prof.a

Document Summary

Chemical and gravitational energy sources could not explain how the sun could sustain its luminosity for more than about 25 million years. The sun shines steadily because nuclear fusion in the core maintains both gravitational equilibrium between pressure and gravity and energy balance between thermal energy released in core and radiative energy lost from the sun"s surface. From inside out, the layers are: core radiation zone convection zone photosphere chromosphere corona. The core"s extreme temperature and density are just right for the nuclear fusion of hydrogen to helium through the proton proton chain. Gravitational equilibrium and energy balance together act as a thermostat to regulate the core temperature because the fusion rate is very sensitive to temp. Randomly bouncing photons carry it through the radiation zone. Mathematical models agree with observations of solar vibrations and solar neutrinos. The stretching and twisting of magnetic field lines near the sun"s surface causes solar activity.