Galaxies Without Dark Matter Challenge Physics

The discovery of a third dark matter–free galaxy, DF9, strengthens the “bullet dwarf” collision theory, suggesting that violent cosmic impacts can separate visible matter from its dark matter halo.

Like earlier finds DF2 and DF4, this ultra-diffuse galaxy shows gravitational behavior explained only by its stars, not unseen mass. The alignment of these galaxies hints at debris from an ancient collision, offering rare evidence that dark matter is a distinct, physical substance—and reshaping our understanding of galaxy formation and the structure of the universe.

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