AST 2002 Lecture Notes - Lecture 11: Photosphere, Strong Interaction, Photon
Document Summary
It is transforming gravitational potential energy into heat. Could be after all, the sun and solar system formed from a contracting cloud. But the mass of the sun could only keep it shining for 25 million years. It is hosting nuclear fusion in its core- here the numbers match up e=mc^2. The energy output of nuclear fusion then stops the contraction. The sun is in a stable phase of equilibrium. Gravitational equilibrium: gravity pulling in balances pressure pushing out. Energy balance: thermal energy released by fusion in core balances radiative energy lost from the surface. Sun: radius: 6. 9*10^8 (109 times earth) mass 2*10^30 (300,00 earths) Solar wind: a flow of charged particles from the surface of the sun. Corona: outermost layer of solar atmosphere ~10^6k - 10^5k. Convection zone: energy transported upward by rising hot gas. Core: energy generated by nuclear fusion ~15 million k. Fusion: small nuclei stick together to make a bigger one. (sun, stars)
