The most precise map of galaxies has confirmed that much of the cosmos is in the dark. The map, which covers 6 percent of the sky and includes 200,000 galaxies recorded by the Sloan Digital Sky Survey, supports previous evidence that most of the universe's matter is invisible. Without the gravity provided by this unseen material, dubbed dark matter, galaxies wouldn't have clustered as tightly as the Sloan map indicates they do.
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