What specific class of pulsating stars served as the essential 'standard candle' for measuring immense cosmic distances?
Answer
Cepheid variables
Cepheid variables were the key standard candles because Henrietta Swan Leavitt established a relationship between their pulsation period and their intrinsic brightness, allowing distance calculation.

Related Questions
Who made the breakthrough measurement determining the true distance to the Andromeda Galaxy (M31) in the early 1920s?What specific class of pulsating stars served as the essential 'standard candle' for measuring immense cosmic distances?What profound relationship did Henrietta Swan Leavitt discover while studying the Magellanic Clouds?What massive telescope did Edwin Hubble use at Mount Wilson Observatory to resolve individual stars in Andromeda?What was the designation given to the specific Cepheid variable star Hubble identified in Andromeda?Before Hubble's findings, what state of scientific understanding characterized the Andromeda Nebula?What was Hubble's initial calculated distance estimate for Andromeda in the 1920s?The concept that allowed Hubble to determine a star's actual energy output (absolute magnitude) using its pulsation cycle is known by what term?What critical concept did Hubble secure by successfully bridging the distance measurement gap between our local stars and intergalactic space?If Andromeda were merely a cloud inside the Milky Way based on the accepted local diameter, how far away would it have been calculated to be?