Why Does the Cepheid "Standard Candle" Have Limited Usefulness Beyond

question 64

Multiple Choice

Why does the Cepheid "standard candle" have limited usefulness beyond 20 Mpc?

• A)Distant galaxies are seen in the past, when Cepheid variables behaved differently than they dotoday.
• B)Distant galaxies are so young they do not contain Cepheids.
• C)Cepheids are too faint to be seen beyond that distance, even with HST.
• D)The light variability of Cepheids diminishes with distance so they do not appear to vary there.
• E)Older distant Cepheids are of Population II, where the period-luminosity relation no longerworks.

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