The universe is full of magnetic fields. Although the universe is electrically neutral, atoms can ionize into positively charged nuclei and negatively charged electrons. When these charges are accelerated, they create magnetic fields. One of the most common sources of large-scale magnetic fields is collisions between and within stellar plasma. It is one of the main magnetic field sources for galactic magnetic fields.

But magnetic fields must also exist on even larger scales. At the largest scale of space, matter is dispersed in a structure known as the cosmic web. Large superclusters of galaxies are separated by barren cavities, like a cluster of soapy water in the middle of a vast region of soap bubbles. Fine fibers of intergalactic material stretch between these superclusters, forming a cosmic web of matter.

Much of this network is ionized, so it should create huge intergalactic but weak magnetic fields. At least that’s the theory. Astronomers have not been able to observe these network magnetic fields. But a new study has discovered them for the first time. We cannot directly detect magnetic fields billions of light years away. Instead, we observe them through their effects on charged particles. Electrons and other particles emit radio light when they spiral along magnetic field lines.

By imaging this radio signal, astronomers can map galactic magnetic fields. But the threads of the cosmic web are so scattered that the radio light they emit is very weak. Too faint to be easily detected. And as nearby galaxies generate even stronger radio signals, the web signal can be suppressed by galactic radio noise.

To overcome this problem, the team focused on polarized radio light. These are radio emissions with a certain directionality. Because the orientation relates to the overall orientation of the filament, the team can more easily extract this signal from the cosmic radio background.

They used data from all-sky radio maps such as the Global Magneto-Ionic Medium Survey, the Planck Legacy Archive, the Owens Valley Long Wavelength Array, and the Murchison Widefield Array. By compiling this data and comparing it with funny network maps, the team verified the polarized radio signal emitted by the network.

This result is not only the first detection of magnetic fields in the cosmic web, but also convincing evidence of the existence of collision shock waves inside intergalactic filaments. These shock waves have been seen in computer simulations of space structures, but this is the first evidence to support the idea that these simulation features are correct.