Overview

• Astronomers measured dispersion in 69 localized FRBs spanning 11.7 million to 9.1 billion light-years to probe unseen ordinary matter.
• They determined about 76% of baryonic matter resides in the intergalactic medium, 15% in galaxy halos and the remainder within stars and cold galactic gas.
• The most distant burst, FRB20230521B at 9.1 billion light-years, served as a key data point for weighing the cosmic web.
• Results align with cosmological simulations and illustrate how supernovae and black hole outflows transport baryons into the intergalactic medium.
• Planned facilities like Caltech’s DSA-2000 are projected to detect up to 10,000 FRBs per year, enabling higher-resolution mapping of diffuse cosmic gas.