What specific class of star was crucial for Edwin Hubble's distance proof for Andromeda?
Answer
Cepheid variable
Hubble's definitive proof that Andromeda was an independent galaxy hinged entirely on identifying a specific class of star: the Cepheid variable. These stars are particularly valuable to astronomers because they pulsate, meaning their luminosity waxes and wanes in a regular, predictable cycle. This pulsation allows astronomers to determine the star's true, intrinsic luminosity (absolute magnitude) once its period is known, which is the key step in calculating its distance using the inverse-square law.
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