Scientists unveil the most detailed map of dark matter to date

Using images from NASA's orbiting Hubble Space Telescope, an international team of astronomers has deduced in unprecedented detail the distributions of dark matter within three clusters of galaxies. They exploited the fact that the gravity of a cluster can distort the images of more-distant galaxies, magnifying them and even making their images multiply, in a process called strong gravitational lensing. Poring over images of a cluster, researchers identified multiple images of dozens of background galaxies. From the distribution and intensities of those images, they then deduced the distribution of dark matter in the cluster. For example, in galaxy MACSJ0416, above, the dark matter distribution consists of a pair of broad, overlapping blobs peppered with hundreds of denser knots enshrouding individual galaxies. The statistical properties of the distribution fit well the predictions of physicists' favored model of "cold" dark matter, which assumes that dark matter consists of heavy, slow-moving particles that do not interact with one another.