Using the NASAHubble Space Telescope's past observations of six massive galaxy clusters, astronomers saw that intracluster light — the diffuse glow between galaxies in a cluster — traces the path of dark matter, illuminating its distribution more accurately than existing methods that observe X-ray light. Hubble's powerful sensitivity and resolution captures a soft blue haze, called intracluster light, among innumerable galaxies in the cluster pictured here. It is the byproduct of interactions between galaxies that disrupt their structures. In the chaos, individual stars are thrown free from their home galaxies to realign themselves with the gravity of the overall cluster. This is also where the vast majority of dark matter, the unobservable material that makes up the majority of the universe, resides. X-ray light indicates where groups of galaxies are colliding, but not the underlying structure of the cluster. This makes it a less precise tracer of dark matter. Credits: NASA, ESA an...