Using NASA?s Hubble Space Telescope, a team of astronomers discovered a ghostly ring of dark matter formed during a collision between two massive galaxy clusters.
The ring, shown in high-resolution maps on NASA?s Web site, may be the strongest evidence that dark matter exists.
The invisible substance has long been proposed as the source of additional gravity that holds together galaxy clusters. Computer simulations of galaxy-cluster collisions created by the team show that when two clusters smash together, dark matter falls inward before sloshing back out. As dark matter moves outward, it begins to slow under the pull of gravity and pile up.
“By studying this collision, we are seeing how dark matter responds to gravity,” team member Holland Ford, also of Johns Hopkins, said in a statement. “Nature is doing an experiment for us that we can?t do in a lab, and it agrees with our theoretical models.”
Although astronomers cannot see dark matter, they can infer its existence by observing how its gravity bends the light from distant background galaxies.
