New self-interacting dark matter could solve three cosmic mysteries

A new self-interacting dark matter theory proposes that dark matter particles collide with one another to form dense cores, potentially explaining three puzzling observations: an ultradense dark matter clump in the gravitationally lensed system JVAS B1938+666, a visible “scar” in the GD-1 stellar stream, and the unusual formation of the Fornax 6 star cluster in the Milky Way’s Fornax dwarf galaxy. The mechanism, related to gravothermal collapse, could unify these disparate clues across cosmic scales in a way standard collisionless dark matter cannot.