ASTR 3 Lecture Notes - Lecture 2: Gravitational Binding Energy, Radiation Zone, Photosphere
Document Summary
Stability requires that at every radius, inward pull of gravity must be balanced by outward push of pressure. P=nkt: n= # of free particles per cubic meter, k= boltz(cid:373)a(cid:374)"s (cid:272)o(cid:374)sta(cid:374)t, p = supports the weight of the gas above r. Gravity depends on the mass within r. Core, radiation zone, convection zone, photosphere: temperature and pressure decrease from core outward less weight there is to support. Center of sun: 15x10^6 k =temp, 160 g/cm^3 =density, pressure = 10^9 atmospheres. Sun is constantly radiating away energy: this heat escape requires an internal energy source as well as heat transport. Governed by second law of thermodynamics: heat flows from hotter body. Stellar heat transport: to colder body radiative: heat carried outward by photons (diffuse or random walk, extremely inefficient: takes about 10^7 years to diffuse from core to surface, does this random walk because it interacts with matter.
