What allows astronomers to confirm that Andromeda is the largest member of the Local Group?
Answer
Its higher star count and potentially larger dark matter halo
While it was previously believed that the Milky Way might be the largest member, precise measurements of stellar populations and rotation speeds have confirmed that Andromeda holds the title. Andromeda contains approximately one trillion stars and possesses a massive halo of dark matter that extends significantly beyond its visible disk, providing the gravitational influence required to hold its own satellite galaxies in orbit.
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Andromeda and the Local Group (go to 2020 4K edition) - YouTube
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