The observational fact about a Cepheid variable star that leads to a measurement of its distance from Earth is that its period of variation is directly related to its
A) surface temperature.
B) position along the spiral arms of a galaxy.
C) apparent magnitude.
D) absolute magnitude.

Question

Quizplus · Accepted Answer

The period of variation of a Cepheid variable star is directly related to its absolute magnitude. This relationship, known as the period-luminosity relation, allows astronomers to determine the distance to the star by comparing its absolute magnitude (intrinsic brightness) with its apparent magnitude (how bright it appears from Earth).

The Observational Fact About a Cepheid Variable Star That Leads