AST201_winter2010_mreid_slideset4_v2_Bb_white

# AST201_winter2010_mreid_slideset4_v2_Bb_white - 1/26/2010...

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1/26/2010 1 AST 201 Stars and Galaxies 1 AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid Other Stars, Continued. .. AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 2 Where Did We Leave Off? How do we determine what stars are like? colour temperature because stars are blackbodies parallax distance for nearby stars luminosity? composition? age? type? AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 3 AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 4 If a star emits light equally in all directions, we on Earth only receive a tiny fraction of it. Call this amount the apparent brightness of the star.

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1/26/2010 2 AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 5 The amount of light you receive from a star falls with the square of your distance from the star. AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 6 This is called the inverse square law of light. So you can determine the luminosity of a star like this: AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 7 distance + app. brightness luminosity How do we figure out what a star is made of? AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 8
1/26/2010 3 AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 9 This is the spectrum of the Sun. It has thousands of absorption lines, as do most stars. AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 10 Edward Pickering of the Harvard College Observatory and his “computers”. An Aside: Women in Science AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 11 Pickering and his associated collected stellar spectra. Each new type discovered was assigned a letter alphabetically: A, B, C, D, etc. This made no sense of them. AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 12

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1/26/2010 4 AST 201, Winter 2010, University of Toronto, Dr. M. A. Reid 13 This is Annie Jump Cannon , the “computer” who finally made sense of the vast catalog of stellar
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## This note was uploaded on 03/02/2010 for the course AST AST201 taught by Professor Mochnacki during the Spring '10 term at University of Toronto- Toronto.

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AST201_winter2010_mreid_slideset4_v2_Bb_white - 1/26/2010...

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