Measuring Light Years: How Far Is the Andromeda Galaxy?

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The Andromeda Galaxy is located approximately 2.2 to 3 million light years from Earth. The distance is measured using methods such as the cosmic distance ladder, which includes techniques like observing Cepheid variable stars. Cepheids are crucial for determining distances to galaxies beyond the Milky Way. These measurements have historically confirmed the existence of other galaxies in the universe. Understanding these distances is essential for comprehending the scale of the cosmos.
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I was reading up on the Andromeda Galaxy and it was saying that it was 2.2 to 3 million light years away from earth. So my question is how do we measure how far it is in light years?
 
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Awesome thank you!
 
In fact, Cepheids were used to establish the fact that galaxies other than the Milky Way actually existed in the universe! re: http://hubblesite.org/newscenter/archive/releases/2011/15
 

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