What did Hubble use to scale galactic and extragalactic distances?
Luminosity and pulsation period of Cepheid variables
Size of galaxy clusters
Brightness of star systems
Distance of comets
Answer
Edwin Hubble used the luminosity and pulsation period of Cepheid variables to scale galactic and extragalactic distances. Cepheid variables are a type of variable star that pulsates in a regular manner, and their luminosity is directly related to their pulsation period. By measuring the pulsation period of a Cepheid variable, astronomers can determine its luminosity, and then use that information to estimate its distance from Earth.
Exploring the Cosmos: Discovering Edwin Hubble's Universe
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