AST201H5 Lecture Notes - Photosphere, Solar Cycle, Chromosphere
Document Summary
Essential cosmic evolution, 5th edition: basic properties of the sun, angular diameter + distance diameter = 109 dearth, volume d3, sun"s mass keeps earth in orbit - law of gravity tells us the sun"s mass = The matter is entirely gas: detailed composition from the amount of light removed by the spectral ab- sorption lines of each chemical element. By mass: 70% h, 28% he, 2% others. By number: 90% h, 9% he, 1% others: luminosity. Measure total radiation arriving at earth above the atmosphere in 1 m2. Assume (now veri ed) that the sun radiates equally in all directions. Total radiation = 3. 8 1026 w. Note, 1 second of the sun"s luminosity would supply all the earth"s energy for 500,000 years: structure of the sun, sun is in balance: pressure outward = gravity inward. Central pressure must be huge to support all the weight: for a gas, pressure and temperature are directly related, t p .
