4232013 uw astr 323 sp13 eric agol 2013 4

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Unformatted text preview: Distance indicators •  Standard ______: know _________ L, measure _____ F g༆ infer distance # D =% !! $ 4π &1 /2 ( ' D = 100.2 (m−M +5) pc !! !! •  Standard ____: know ______ R g༆ measure € _________ size α g༆ infer distance € " % D =$ !! # 4/23/2013 ' & UW, ASTR 323, SP13, Eric Agol ©2013 4 Galac8c distance ladder 1.  Radar ranging – only works in _____ ______ 2.  Parallax – only works out to ~___ pc 3.  Moving cluster – works out to ~3 kpc 4.  Main- sequence fi_ng – e.g. Pleiades is 7.5 8mes fainter than Hyades, so distance ra8o is _____ – works out to ~100 kpc (SMC/LMC) (Each step depends on prior, so uncertain8es grow) 4/23/2013 UW, ASTR 323, SP13, Eric Agol ©2013 5 Extragalac8c distance ladder Standard candles: 1.  Cepheid variables – common; depends on metallicity/ex8nc8on; 30 Mpc 2.  Tully- Fischer rela8on - spirals-...
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