Two galaxy clusters, Abell 0399 and Abell 0401, are merging about 1 billion light-years from Earth. This image shows the clusters’ cores (red) in X-ray-light. The two are linked by a thin filament (yellow and blue), which glows faintly in microwaves and radio waves. (Credit: DSS and Pan-STARRS1 (optical), XMM-Newton (X-rays), PLANCK satellite (yparameter), F. Govoni, M. Murgia, INAF)

Galaxy clusters are a great place to peer in on the physics that govern our universe. Not only are these cosm