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Question
Why did Hubble have to rely on Cepheids to find the distance to M31, unlike Shapley's use of RR Lyrae stars with the Milky Way?Answer
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Related questions
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The spiral arms are blue from the presence of Population ________ stars in them.
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Why is the energy source for active nuclei like Seyferts thought to be compact?
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B) Their energy appears to be non-stellar synchrotron radiation.
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Why aren't there young stars in the halo?
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What advantage do radio astronomers have over optical ones in mapping the entire Milky Way?
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