Lec+22 - Lecture 22 The Universe(B 1 Expansion of the...

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Lecture’22’ ’’ The Universe (B) ±
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Expansion’of’the’Universe This’ expansion ’was’discovered’by’ Edwin’ Hubble ’when’he’measured’the’ veloci<es’of’galaxies.’ Rela<vis<c’Doppler’eFect:’ Wavelengths’from’receding’light’ sources’are’always’shi±ed’toward’ longer wavelengths .’This’increase’in’ wavelength’is’called’the’ red shi: .’ ± Mt.’Wilson’100-Inch’Telescope:’ hJp://www.astrosurf.com/re/ritchey_1929_plate31.jpg hJp://www.oneminuteastronomer.com/wp- content/uploads/2012/03/Edwin-Hubble.jpg "The history of astronomy is a history of receding horizons.” ~’Edwin’Hubble’ ’(1889-1953)’ hJp://deskara<.com/wp-content/uploads/2012/11/red-shi±.jpg
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Expansion’of’the’Universe’ ± hJp://www.youtube.com/watch?v=hVApTLE7Csc
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Expansion’of’the’Universe § Units’of’ v :’km/s’(kilometers’per’ second).’ § Unit’of’ r :’ Mpc’( megaparsec,’ a’ length’unit’commonly’used’in’ astronomy’and’astrophysics). ’ § H 0 ’is’the’ Hubble constant ’(an’ empirical’quan<ty)’which’ is’ constant over space at any =me .’ ± Analysis’of’redshiDs’from’many’distant’galaxies’led’Hubble’to’ the’conclusion:’ The recession speed v of a galaxy is propor=onal to its distance r from us .’ v = H 0 r ( Hubble’s Law )’ H 0 = 71 km/(s ! Mpc)
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Expansion’of’the’Universe ± 1- arcsecond ’=’1/3600 o .’ 1’ AU ’( astronomical unit )’=’1.5’x’10 11 ’m’=’average’Earth-Sun’separa<on.’ 1’ ly ’( light-year )’=’9.46’x’10 12 ’km’=’the’distance’light’travels’in’1’year.’ 1’ pc ’( parsec )’is’the’distance’at’which’there’is’1-arcsecond’angular’ separa<on’between’two’objects’1’AU’apart.’ 1’pc’=’3.26’ ly;’1’ Mpc’=’3.26’x’10 6 ’ ly.’ hJp://www.school-for-champions.com/astronomy/images/astronomical_distances-parsec.gif hJp://physics.syr.edu/courses/CCD_NEW/se</tutorial/measure/images/parallax.jpeg ’(ModiFed)’ hJp:// upload.wikimedi a.org/wikipedia/ commons/d/d7/ Protractor_Rapp orteur_Degree_ V1.jpg 1 pc
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The’Hubble’Space’Telescope’ ± Determining’the’Hubble’ constant’has’been’the’key’goal’ of’the’ Hubble Space Telescope ,’which’can’measure’ distances’to’galaxies’with’ unprecedented’accuracy.’
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Lec+22 - Lecture 22 The Universe(B 1 Expansion of the...

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