Astronomers are making significant strides in comprehending how matter behaves and interacts in space utilizing fast radio bursts (FRB). They have found that over three-quarters of the universe’s ordinary material is concealed within sparse intergalactic gases, and they have also identified the furthest FRB event recorded to date.
This artist’s concept illustrates the density regions and red blank areas of the universe’s web in blue. Image Credit: Jack Madden/Illustristng/Ralf Konietzka/Liam Connor, CFA.
For many years, it has been established that at least half of the normal, predominantly proton-based baryonic material in the universe has gone unaccounted for.
Previous approaches by astronomers employed methods like X-ray and ultraviolet observations to gather significant clues regarding this missing mass, which manifests as extremely thin warm gases between galaxies.
The challenge arises from the high-temperature, low-density gas that remains mostly invisible to most telescopes, leaving scientists unable to assess its presence or distribution.
This is where FRBs come into play – brief, intense radio signals emitted by distant galaxies that researchers have recently demonstrated could measure baryonic matter in space, although its location remained a mystery until now.
In the latest study, scientists examined 60 FRBs, with the most distant FRB recorded at 1,174 million light-years (FRB 20200120E) from Messier 81 and reaching up to 9.1 billion light-years (FRB 20230521b).
This enabled them to pinpoint the missing material within intergalactic spaces or the intergalactic medium (IGM).
“The ‘baryon problem’ was never in doubt,” stated Dr. Liam Connor, an astronomer at the Harvard & Smithsonian Center for Astrophysics. “The issue has always been about its location. Now with FRBs, we’ve established that three-quarters of it exists between galaxies in the cosmic web.”
By analyzing the delays in each FRB signal as it traveled through space, Dr. Connor and his colleagues tracked the gaseous medium along its path.
“FRBs function like flashlights in space, illuminating the intergalactic medium. By accurately gauging how the light slows down, we can assess this medium, whether it’s starkly visible or barely detectable,” Dr. Connor explains.
The findings are revealing—approximately 76% of the universe’s baryonic matter resides within the IGM.
Additionally, about 15% is found in galaxy halos, with a minor fraction embedded within stars and cool galactic gases.
This distribution aligns with predictions made by advanced cosmological simulations, yet this is the first instance of direct confirmation.
“This marks a triumph for contemporary astronomy,” noted Dr. Vikram Ravi, an astronomer from California.
“Thanks to FRBs, we are now approaching a new understanding of the universe’s structure and composition.”
“These brief flashes enable us to trace the invisible baryonic matter filling the expansive voids between galaxies,” he added.
“Baryons are pulled into galaxies by gravity; however, supermassive black holes and supernova explosions can expel them back into the IGM, cooling cosmic temperatures when they spiral out of control,” commented Dr. Connor.
“Our findings indicate that this feedback mechanism is effective, suggesting gas must be displaced from galaxies into the IGM.”
The team’s results are published today in the journal Nature Astronomy.
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L. Connor et al. Gas-rich cosmic web unveiled by the partition of missing baryons. Nature Astronomy Published online on June 16th, 2025. doi:10.1038/s41550-025-02566-y
Source: www.sci.news
