Suppose we observe a Cepheid variable in a distant galaxy.The Cepheid brightens and dims with a regular period of about 10 days.What can we learn from this observation?
A)It will allow us to calculate the rotation rate of the galaxy.
B)It will allow us to determine the mass of the galaxy.
C)We can learn the distance to the galaxy.
D)Under the rules of the International Astronomical Union,we will be entitled to naming rights for the galaxy.

Question

Quizplus · Accepted Answer

The regular period of brightening and dimming of a Cepheid variable is directly related to its luminosity. By measuring the period of a Cepheid variable, we can determine its true luminosity and compare it to its apparent brightness as seen from Earth. This allows us to calculate the distance to the galaxy in which the Cepheid variable is located. Therefore, option C is correct. Option A and B are incorrect as the rotation rate or the mass of the galaxy cannot be determined solely from the observation of a Cepheid variable. Option D is absurd and incorrect.

Suppose We Observe a Cepheid Variable in a Distant Galaxy