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Parallax only works for nearby stars
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Spectroscopic Parallax works somewhat further out
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Measure spectra and get Spectral Type and Luminosity
Class
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From those get Luminosity and then use m-M to find
distance
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Limited because need relatively bright stars to get
high resolution
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spectra
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Need another way to find M, then use m-M to get
distances
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Variable stars and the Period-Luminosity
relationship:
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Some stars vary in intrinsic brightness with time
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The larger, more massive, and brighter stars vary more slowly
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Like the relative pitch of a large vs. small
organ pipe
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