ASTR 3 Lecture Notes - Lecture 11: Stay Cool, Gravitational Energy, Convection Zone
Document Summary
Sun first believed to generate energy by slowly contracting in size in process called gravitational contraction. Gravitational potential energy converts to thermal energy as gas moves inward. Sun shines by converting mass into energy through nuclear fusion. Nuclear fusion requires high temperatures and densities. Gravitational contraction released the energy that made the sun"s core hot enough for fusion inward pull of gravity. Gravitational equilibrium is balance between the outward push of internal gas pressure and. Pressure greatest deep in sun where overlying weight is greatest pressure sustains nuclear. Energy balance is balance between rate at which fusion releases energy in sun"s core and the fusion rate at which sun"s surface radiates this energy into space. Without it, balance of pressure and gravity don"t remain steady. Differing temperatures and densities of plasma at different depths give sun layered structure. Sunspots are blotches on surface of sun appearing darker than surrounding regions. Entire sun does not rotate at same rate.
