Milky Way's gravity may mimic dark matter signals, simulations reveal

For decades, astronomers have traced the long ribbons of stars torn from dwarf galaxies—called stellar streams—hoping to read in their shapes the invisible hand of dark matter. New computer simulations, born from a quiet reexamination of an old Hubble image, now suggest that the Milky Way's own ordinary gravity can sculpt those same shapes, producing signals indistinguishable from what dark matter would leave behind. The universe, it seems, is a more ambiguous witness than science had hoped—and the search for its hidden matter must now contend with the galaxy's own mimicry.