Astronomy 1021 Lecture 2: Sem 2 Week 2

• School: Western University
• Department: Astronomy
• Course: Astronomy 1021
• Professor: Robert Cockcroft

Document Summary

For thermal radiation at a given temperature, the star needs to be of a certain size to result in the observed luminosity. So two stars with the same temperature, but different luminosities must have different radius. Most of the stars, including the sun have properties (luminosity, temperature) that put them on the main sequence. Main sequence forms a line which means that all main sequence stars share a particular relationship between luminosity and surface temperature. Because a star is the continuing ght of a self gravitating mass of gas against gravity. Wednesday, january 18, 2017: the sun is in hydrostatic equilibrium; outward pressure (fusion) = inward force of gravity, more massive stars must produce more energy to balance the stronger gravity. Since luminosity = energy produced, we see how a more massive star will have a higher luminosity. More energy also mens higher surface temperature. Initial mass also determines a star"s ms lifetime.