Nobody knows the real nature fast radio bursts (FRB). But these ultra-short bursts of radio waves are starting to shed light on the structure of galaxies and the evolution of the universe. When flares occur in deep space, astronomers learn about the cosmic distribution of dilution. ionized gas – a plasma consisting of atomic nuclei and free electrons – almost impossible to observe directly.

“Astronomers love a good mystery – what is an FRB? – but the broader impact of FRBs on astrophysics will certainly come from their application as unique probes of the dark baryonic universe,” says Ziggy Pleunis (University of Toronto). Dark baryons are not the same as dark matter, they are just hot and therefore almost invisible gaseous ions that surround galaxies and permeate intergalactic space.

Pleunis is part of a large, mostly Canadian team of astronomers studying fast radio bursts with the Canadian Hydrogen Density Mapping Experiment (CHIME) telescope in British Columbia. A detailed analysis of 93 FRBs detected by CHIME has been published. Astrophysical Journalshows that the halo of our own Milky Way galaxy contains less baryonic matter than most models of galaxy evolution predict.

FRBs are most likely energetic bursts on or near highly magnetized neutron stars in distant galaxies and emit radio waves over a wide frequency range. These waves slow down slightly when interacting with the plasma between the distant blast and Earth, and high-frequency waves slow down more than their low-frequency counterparts. As a result, the spikes, which usually last no more than a millisecond, eventually disappear. This dispersion measure greater if there is more interstitial plasma.

In this way, astronomers can use FRBs as searchlights to shine light on gas between and around galaxies. “Each FRB gives us measurements of the Milky Way halo in one direction, so by continuing to add them we can build a detailed picture,” team leader Amanda Cook (University of Toronto) explains in a press release.

The team’s analysis appears to confirm previous results based on a single FRB observed at the Deep Synoptic Array-110 observatory under construction in California and presented by Vikram Ravi (California Institute of Technology) at the American Astronomical Society meeting in Seattle. At the time, Ravi explained the discrepancy between observations and theory by suggesting that the Milky Way halo may have lost baryonic matter over time. Supernova explosions and strong stellar winds can blast gas beyond the gravitational reach of our galaxy.