... Gravitational wave search provides insights into galaxy evolution and mergers . ... galaxies . ... Astronomers probe "sandbar" between islands of galaxies . ... The hot gas filling the cluster and filament is illustrated with purple. ... The leftover gas is strewn in filaments between galaxy clusters. ... The technique by Edwards and her colleagues, which uses radio frequencies that can reach a host of ground-based telescopes, points to an easier way to probe the interiors of galaxy-cluster...