Why is cosmological redshift different from the red color of cool, old stars?
Answer
Cosmological redshift affects the entire spectrum of a galaxy regardless of star types
While elliptical galaxies may contain populations of old, cool stars that appear red due to their lower temperatures, this is an intrinsic property of the star itself. Cosmological redshift is a distinct, external phenomenon that affects all light emitted by a galaxy, including the light from gas, dust, and all star types present. It shifts the entire spectral fingerprint of the galaxy rather than just changing the color of specific stars.
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