This fast radio burst shined a light on a galaxy’s mysterious gas halo
A lucky alignment let astronomers use a bright blast from one galaxy to probe gas in another

A fast radio burst from a small, distant galaxy (upper left) passed through the halo of a more massive galaxy (center) before reaching telescopes on Earth (blue dot), as seen in this illustration. The yellow line traces the FRB’s path (arrow denotes direction) and the kink illustrates the energy pulse at one point of its journey.
J. Josephides/Centre for Astrophysics and Supercomputing/Swinburne University of Technology