OUR galaxy may be embedded in a pancake of dark matter, so dense it is easier to detect than conventional dark matter.

Most astronomers believe a spherical cloud of dark matter envelops our galaxy. Though invisible, its gravity perturbs the visible stuff. Now there may also be a pancake of dark matter.

Calculations by Tobias Bruch of the University of Zurich, Switzerland, and colleagues suggest that when the Milky Way devours smaller galaxies, their dark matter should get caught in its disc of stars and gas. This would form a pancake that Earth-based experiments would find easier to spot because …