Question 20 • Earth and Space Science
Cepheid variables are useful distance indicators within the Milky Way and beyond because their pulsation periods reveal their luminosities. Comparing a Cepheid’s known luminosity with how bright it appears lets astronomers estimate its distance, including at 50,000 light-years. Parallax is generally useful over much shorter distances, while type Ia supernovae and redshift are mainly used for much more distant objects.
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