a) Cepheids are variable intensity stars that are used to determine how far away a distant galaxy is from Earth. b) The redshift of the spectral line in the light from a distant star indicates that the star is moving away from us. c) The acceleration of the universe's expansion rate is thought to be due to the existence of dark energy. d) As we look at more distant stars, we are actually looking at the past universe. e) It is widely thought that a black hole is located at the center of most galaxies.
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