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The Milky Way and Andromeda galaxies are approaching each other. With current technology, how long would it take before we could directly measure the apparent increase in size of Andromeda?

Allan Burger, Passaic, New Jersey
RELATED TOPICS: MILKY WAY | ANDROMEDA GALAXY
Andromeda and Milky Way galaxies
In the next several billion years, our Milky Way Galaxy will merge with the neighboring Andromeda Galaxy, which is now some 2.5 million light-years away. Currently, Andromeda’s disk of stars is a few times bigger than the apparent size of the Full Moon, covering a few degrees on the sky (depending exactly on where you draw its edge).

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