For the first time, astronomers have sighted magnetic fields between two galaxy clusters — a find that suggests some of the largest scale structures in the universe are magnetized.
The fields run between the galaxy clusters Abell 0399 and Abell 0401, which are beginning to merge about 1 billion light-years from Earth, researchers report in the June 7 Science. Radiation from electrons zipping through the magnetic fields revealed this magnetism inside the gaseous filament that connects the clusters in the cosmic web (SN: 3/8/14, p. 8). The source of those high-speed particles, however, remains a mystery.