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This puzzling result makes sense if one assumes that the boundary stars are feeling the gravitational effects of an unseen mass—dark matter—in a halo around the galaxy. Dark matter could also ...

New research suggests that they could hold giant "dark stars," or invisible clumps of matter. Most of the mass in any galaxy is invisible, so astronomers do not yet know the identity of the dark ...

But, not all galaxies are created equal, it seems, as astronomers have discovered what they believe is a “dark galaxy,” a galaxy that doesn’t give off visible light. In most cases ...