In determining the distance to a galaxy by using observations of a Cepheid variable star, which of these properties is NOT needed?
A) average brightness or apparent magnitude of the Cepheid
B) velocity of the Cepheid via the Doppler effect
C) type of spectrum of the Cepheid-whether it is metal-rich or metal-poor
D) period of variability of the Cepheid

Question

Quizplus · Accepted Answer

The velocity of the Cepheid via the Doppler effect is not needed to determine the distance to a galaxy. The distance is calculated using the period-luminosity relationship, which requires the period of variability and the apparent magnitude.

In Determining the Distance to a Galaxy by Using Observations