Technology explainer
How Do Fast Radio Bursts Reveal Invisible Matter?
Fast radio bursts pass through diffuse gas on their journey to Earth. By measuring how that gas delays different radio frequencies, astronomers can estimate otherwise invisible matter between and around galaxies.
Much of the universe's ordinary matter is difficult to see because it exists as thin, hot gas rather than bright stars. Fast radio bursts provide a way to measure that hidden material.
What is a fast radio burst?
A fast radio burst is a millisecond-scale pulse of radio energy from a distant source. Some repeat, while others have been detected only once.
What happens as the signal travels?
Free electrons in intervening gas slow lower radio frequencies slightly more than higher frequencies. This produces a measurable spread called dispersion.
How does dispersion reveal matter?
The amount of dispersion depends on the number of free electrons along the path. After accounting for the Milky Way and the source galaxy, astronomers can estimate matter in intergalactic and circumgalactic space.
What can the method not show directly?
Dispersion measures total electrons along a line of sight, not a detailed three-dimensional map by itself. Researchers need many bursts with known distances and directions.
Why are larger samples important?
Thousands of localized bursts can reveal how ordinary matter is distributed around different galaxies and test models of cosmic structure.
First appeared in
Astronomers Used Cosmic Radio Flashes to Find Matter That Had Vanished From the Universe
