A persistent cosmic mystery has been resolved as researchers have successfully located the missing ordinary matter that has eluded astronomers for decades. According to a study published in the journal Physical Review Letters, the missing mass exists in the form of highly diffuse gas clouds, or “puffs,” that surround groups of galaxies.
Scientists Locate Missing Ordinary Matter in Diffuse Cosmic Clouds
For years, astrophysicists have grappled with a discrepancy between the amount of ordinary matter predicted to exist shortly after the Big Bang and the amount actually observed in the universe today. Estimates indicate that roughly 17% of the early universe consisted of baryonic matter—the family of subatomic particles including protons and neutrons that constitute stars, planets, and galaxies. However, the total mass of all visible objects in the universe accounts for only about 10% of that initial 17%. The remaining 90% of expected baryonic matter had been missing, leaving scientists to search for its location.
Utilizing Fast Radio Bursts as Cosmic Probes
To track this elusive material, an MIT-led team within the CHIME/FRB Collaboration developed a new method using fast radio bursts (FRBs). First detected in 2007, FRBs are ultrabright, millisecond flashes of radio waves originating from distant, highly energetic phenomena.
As these signals travel through space, they interact with matter, causing the radio waves to smear out in time. Fast radio bursts start out as a very quick flash, and as they pass through matter, they smear out in time,
explained Haochen Wang, a graduate student in MIT’s Kavli Institute for Astrophysics and Space Research. And we can measure that smearing very precisely, which is directly proportional to how much missing matter the FRB passed through.
By analyzing thousands of FRB measurements and comparing the degree of signal smearing against the known locations of galaxies, researchers were able to distinguish between matter contained within galaxies and the missing matter located in the surrounding space.
Findings Reveal Unexpectedly Large Galactic Environments
The study’s results indicate that the missing baryonic matter is scattered in diffuse clouds at densities as low as one proton per cubic meter. These clouds extend up to 4 million light-years away from galaxy groups, a distance significantly further than existing astrophysical models had predicted.
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A galaxy is maybe a few 100,000 light years across, and we found missing matter out to about 4 million light years,
said Kiyoshi Masui, an associate professor of physics at MIT. According to Masui, these findings suggest that the processes responsible for moving this matter—such as black hole jets and exploding stars—are more violent and energetic than previously thought. These galactic fountains
effectively push gas out of galaxies and across vast cosmic distances.
Implications for Future Astrophysical Research
The discovery provides researchers with a new way to map the distribution of matter in the universe, which is essential for understanding how galaxies form and interact with their environments.
We’re not just probing if the gas is with the galaxy or not, but we are seeing the shape of the missing matter that’s around the galaxies,
Wang noted. By mapping these shapes, scientists hope to gain a clearer picture of galactic evolution.
While the current study successfully demonstrates the viability of using FRBs to locate baryonic matter, researchers emphasize that there is still much to learn about both the missing matter and the nature of the fast radio bursts themselves. As more data becomes available, the team expects to refine their measurements, allowing for even greater precision in mapping the structure of the universe.
For further details on this research, see the reports from Gizmodo and MIT News.
