ASTRON 100 Lecture Notes - Lecture 12: Photon, Thermostat, Gravitational Collapse
7 Sep 2016
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Sun"s energy: we only get a small fraction of this energy, fraction = pi r^2 / 4/3 pi (1 au)^2, = 1. 36 x 10^-9, the solar constant is 1367 w/m^2, solar panels are about 22% efficient. 10. to generate 10^20 j of energy with solar power in a year we need 10. 5 billion m^2 of solar panels = 63 mi x 63 mi: we could spread them out on rooftops across the us. 12. energy problem is solvable if we"ll spend the money the sun: our star. 13. the sun is an ordinary star and shines the same way other stars of its type do. 14. the bright part normally seen is called the photosphere, which is about 500 km deep. 15. it is an almost perfect blackbody with a photosphere temperature of 5800 k the solar spectrum. 16. spectrum known as fraunhofer lines: made of hot gas, mostly hydrogen and helium.
