Which variable star type is crucial for measuring cosmic distances due to its Period-Luminosity relation?
Answer
Cepheid variables
Certain types of pulsating variable stars act as indispensable tools for astronomers to map the galaxy and universe. Specifically, Cepheid variables exhibit a precise relationship between the period of their pulsation and their actual intrinsic luminosity, known as the Period-Luminosity relation. By measuring how fast a distant Cepheid pulses, an observer can accurately determine its true brightness. Comparing this known absolute brightness with its measured apparent brightness allows for a direct and highly accurate calculation of the vast distance to that star and its host system, a measurement otherwise fraught with difficulty.
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