A magnetic field with a strength of just 0.00000000000000028 Gauss has been found filling the vast, empty voids between galaxies.
April 25, 2026
Original Paper
Search for Anisotropic Pair Halos Associated with Blazar Jets
arXiv · 2604.19916
The Takeaway
Astronomers detected this incredibly faint field by looking at the halos of gamma-rays surrounding distant, bright galaxies called blazars. These halos are slightly lopsided, which proves that a magnetic field is pushing against the light as it travels through intergalactic space. This measurement gives us a concrete look at the large-scale structure of the entire universe. It shows that even the emptiest parts of space are not truly empty, but are permeated by ancient magnetic forces. Understanding these fields is essential for figuring out how the first stars and galaxies were originally formed.
From the abstract
The origin of intergalactic magnetic fields (IGMFs) remains one of the key open questions in cosmology. Gamma-ray pair halos produced by electromagnetic cascades from TeV-emitting blazars provide a powerful indirect probe of these fields. In this work, we present a novel search for pair halos that explicitly exploits their expected anisotropic morphology, aligning with the projected orientation of blazar jets on the sky. Using a Monte Carlo framework to model the spatial distribution of cascade