A fast radio burst is a short but powerful flash of radio waves from deep space. As it travels to us, the signal passes through clouds of tenuous gas, and the more gas it encounters, the more the signal is smeared across frequencies. Astronomers call this delay the dispersion measure — essentially, it's a "weighing" of all the matter along the line of sight.

But here's the catch: for most bursts, we don't know how far away they are. Without that, it's unclear where exactly the gas was encountered. The authors of the study propose a clever statistical trick to get around this. Instead of determining the distance for each burst individually, they cross-correlate two datasets: a list of bursts with their dispersion measures and a galaxy map with known distances. This cross-analysis, akin to finding matches between two long lists, captures common patterns — where there are more galaxies, the signal delay is on average larger.

The researchers compared two versions of this cross-correlation. The old method worked directly with the dispersion measure, while the new one splits bursts into groups by delay magnitude and looks for a correlation with galaxies for each group. It turns out the second approach is far more sensitive. For a sample of 1600 bursts, roughly what the CHIME telescope has gathered, it yields a signal-to-noise ratio of about 12. And for future 20 000 bursts from the CHORD facility, it reaches 54. That means the signal stands out very clearly against random noise.

The main practical takeaway: the method promises to measure an important parameter — the scale at which feedback from stars and black holes "blows out" gas and prevents it from clumping. With current data, the precision will be 26%, and with future data, 14%. This is a window into the physics of how galaxies exchange matter with their surroundings. And all this without a single precise distance to the bursts themselves.