What specific type of star did Hubble analyze to measure the distance to the spiral nebulae?

Answer

Cepheid variable stars

Hubble focused on identifying Cepheid variable stars within the nebulae. He utilized the established relationship, developed by Henrietta Swan Leavitt, between a Cepheid’s pulsation period and its true intrinsic brightness to calculate distance.

What specific type of star did Hubble analyze to measure the distance to the spiral nebulae?
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