Astronomy Practice Exam

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What characteristic is specific to Cepheid variable stars?

They are always the same color
They change brightness predictably over time
They are located exclusively in our galaxy
They are used for measuring star temperatures

The correct answer is: They change brightness predictably over time

Cepheid variable stars possess a unique characteristic of changing brightness in a predictable manner over time. This variability occurs due to regular pulsations in their size and temperature, which directly correlates with their luminosity. This property allows astronomers to measure their light curves accurately, leading to a reliable period-luminosity relationship. Because of this relationship, Cepheid variables serve as crucial "standard candles" in astrophysics, helping to determine distances to far-off galaxies. Their predictable brightness variations make it easier for researchers to understand stellar evolution and the structure of the universe. The other characteristics mentioned do not accurately define Cepheid variable stars; they can exist in various colors, are found in numerous galaxies, and are not specifically used to measure temperatures of stars.