Dark matter core, left behind from wreck between massive clusters of galaxies, defies explanation

Astronomers using data from NASA’s Hubble Telescope have observed what appears to be a clump of dark matter left behind from a wreck between massive clusters of galaxies. The result could challenge current theories about dark matter. Dark matter is not behaving as predicted, and it’s not obviously clear what is going on. It is difficult to explain this Hubble observation with the current theories of galaxy formation and dark matter.

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