Distances to a nearby galaxy can be determined MOST accurately by
A) measuring the periods of pulsating stars.
B) measuring the chemical compositions of the brightest stars.
C) measuring the shifts of spectral lines from the Milky Way Galaxy.
D) measuring the total amount of energy received from the Milky Way Galaxy.

Question

Quizplus · Accepted Answer

Measuring the periods of pulsating stars, such as Cepheid variables, is a highly accurate method for determining distances to nearby galaxies. The period-luminosity relationship of these stars allows astronomers to calculate their absolute brightness, and by comparing this to their apparent brightness, the distance can be determined. This method is not dependent on the chemical composition of stars (B), nor does it involve measuring shifts of spectral lines from the Milky Way Galaxy (C) or the total amount of energy received from the Milky Way Galaxy (D), which are less direct or less accurate methods for determining distances to other galaxies.

Distances to a Nearby Galaxy Can Be Determined MOST Accurately