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11:10:09 Our Milky Way Galaxy and Other Galaxies

11:10:09 Our Milky Way Galaxy and Other Galaxies - 08:35:00...

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Our Milky Way Galaxy and Other Galaxies 10/11/2009 08:35:00 What went wrong? Absorption by dust o Flux o Absorption reduces Flux o Dust absorbs more in blue than in red o Use colors to sort out dust from distance Mapping Out the Galaxy What do we know about the different parts of our Milky Way Galaxy o Need distances to figure out how big it is and where things are Key Elements o Parallax only works for nearby stars o “Standard Candles” – objects of known luminosity. Observe flux, then  get distance o Want them to be intrinsically bright and good standards. Cepheid  variable stars standard candles of choice Pulsating Variable Stars These stars regularly expand and contract Like a big spring Change in size o Change in luminosity Cepheid variable stars with longer periods have greater luminosities (P-L  relation)
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