In Determining the Distance to a Galaxy by Using Observations

question 121

Multiple Choice

In determining the distance to a galaxy by using observations of a Cepheid variable star,which of the following is NOT needed?

• A) The star's velocity via the Doppler effect
• B) The Cepheid's period of variability
• C) The type of spectrum of the Cepheid: metal-rich or metal-poor
• D) The star's average brightness or apparent magnitude

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