👤 whose
Whose work first showed that galaxies are outside the Milky Way?
Quick Answer
Edwin Hubble’s. He identified Cepheid variables in Andromeda in 1923–24, proving it is a separate galaxy.
The Full Story
Using the 100-inch Hooker Telescope, Edwin Hubble found Cepheid variable stars in the Andromeda “nebula.” Cepheids have a known period-luminosity relation, which lets astronomers measure distance. Hubble’s distance estimate showed Andromeda was far beyond the Milky Way, making it a separate galaxy. This discovery dramatically expanded the known scale of the universe.
Key Facts
1.Key discovery in 1923–1924
2.Andromeda is about 2.5 million light-years away
3.Used Cepheid variable stars
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Suggested video title for this topic:
"The observation that turned a nebula into another galaxy"
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