Brilliant Darkness

Observations of Abell 383, a giant cluster of galaxies about 2.3 billion light-years from Earth, shows how dark matter is concentrated in the cluster's center. This image combines optical light from ground- and space-based telescopes (blue and white) with X-ray data from the Chandra X-Ray Observatory (purple). The X-rays show the glow of superhot gas. The optical reveals a gravitational lensing effect, which produces the arc-shaped structures. The arcs are projections of background galaxies that are distorted by the combined gravity of the cluster's galaxies and its dark matter -- a type of matter that produces no detectable energy, but that reveals its presence through its gravitational pull on the material we can see. Careful study of the cluster shows that the dark matter is distributed in a region that's shaped something like a football. [NASA/CXC/Caltech/A.Newman et al/Tel Aviv/A.Morandi & M.Limousin/STScI/ESO/VLT/SDSS]