What role do Cepheid variables and Type Ia supernovae serve in calibration?
Answer
They are standard candles whose intrinsic luminosity is known.
Cepheid variables and Type Ia supernovae are invaluable to cosmology because they function as 'standard candles.' A standard candle is an astronomical object whose true, or absolute, magnitude—its intrinsic luminosity—is known independently of its observed brightness. By comparing this known absolute magnitude with the apparent magnitude measured from Earth, astronomers can calculate the object's distance with a relatively high degree of accuracy. This calibration forms crucial upper rungs on the cosmic distance ladder, allowing for the estimation of distances to remote galaxies.
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