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 determine the mass of the galaxy.
B)Under the rules of the International Astronomical Union, we will be entitled to naming rights for the galaxy.
C)It will allow us to calculate the rotation rate of the galaxy.
D)We can learn the distance to the galaxy.

Question

Quizplus · Accepted Answer

The regular period of the Cepheid variable allows us to use it as a standard candle, which means we can use its brightness to determine the distance to the galaxy it is located in. This is because the brightness of a Cepheid variable is directly related to its period. Therefore, option D is the correct answer. Options A and C are unrelated to the observation of a Cepheid variable, and option B is not a scientific outcome of observing a celestial object.

Suppose We Observe a Cepheid Variable in a Distant Galaxy