AST201H1 Lecture Notes - Lecture 4: White Dwarf, Main Sequence, Luminate
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Ast201: building the h-r diagram ( chp 15. 2) Recall: the set of lines present in a star"s spectrum tell us the star"s chemical composition. You can have vans and trucks that are red, smartcars that are red, small cars that are red. H-r diagram provides direct info about stellar radii bc star"s luminosity depends on both its surface temperature and its surface area (or radius) If 2 stars have same surface temperature, one can be more luminous than the other only if its larger in size. Radii increases as we go from high temperature, low luminosity corner on the lower left of h-r diagram to low temperature, high luminosity corner on the upper right (radius increases from lower left to upper right) Notice for eg. betelgeuse and adebaran have less surface temperature than the sun but bc they are much bigger, they luminate more. Supergiant like betelgeuse would fill the inner solar system.