Problem 7

Given information

Given that Cepheid variable stars change in luminosity with a typical period of several days and the period has been found to have a definite relationship with the average intrinsic luminosity of the star we are asked how these stars could be used to measure the distance to galaxies.

Step-by-step explanation

Calculate the period of a Cepheid variable star's changing luminosity. To determine its absolute luminosity, use the well-known relationship between period and luminosity. To determine the distance to the galaxy in which it is located, compare its absolute luminosity to its apparent brightness (the observed brightness).