To get the distance to a Cepheid variable star, astronomers must take several steps. Which of the following is NOT one of these steps?
A) observe the star getting brighter and dimmer to establish that it varies
B) measure the period of variations by timing when the star is brightest and dimmest
C) estimate the apparent brightness of the star
D) measure the star's Doppler shift from its spectrum
E) apply the period-luminosity relationship

Question

Quizplus · Accepted Answer

Measuring the star's Doppler shift is not necessary for determining the distance to a Cepheid variable star. The other steps listed (observing the star's brightness variations, measuring the period of those variations, estimating the star's apparent brightness, and applying the period-luminosity relationship) are all important steps in determining the distance to a Cepheid variable star.

To Get the Distance to a Cepheid Variable Star, Astronomers