ASTR 001 Lecture 10: Our Star
Document Summary
Gravitational contraction: provided energy that heated core as sun was forming contraction stopped when fusion began. Gravitational equilibrium: energy provided by fusion maintains the pressure. In the sun, an exact balance between the inward pull of gravity and the outward pressure of energy release is maintained. Also, the sun radiates from its surface exactly as much energy as it produces in its core: making mathematical models. Overall, the sun is not noticeably expanding or shrinking. This precise balance of inward and outward pressure is called hydrostatic equilibrium. Simply knowing that this exists allowed us to begin constructing theoretical models of the interior of the sun: observing the sun quakes. Patterns of vibration on surface tell us about what sun is like inside. Results agree very well with mathematical models of solar interior: observing solar neutrinos. Neutrinos created during fusion fly directly through the sun. Observations of these solar neutrinos can tell us what s happening in core.
