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15h ago

Fast Radio Bursts Reveal 75% of Universe’s Missing Ordinary Matter

Published in Nature Astronomy, the new study measured dispersion in dozens of FRBs across billions of light-years to map the elusive web of intergalactic gas.

Image
Image
This artist's conception depicts a bright pulse of radio waves, or fast radio bursts, on its journey through the fog between galaxies, known as the intergalactic medium. Long wavelengths, shown in red, are slowed down compared to shorter, bluer wavelengths, allowing astronomers to "weigh" the otherwise invisible ordinary matter.

Overview

  • Astronomers led by Liam Connor and Vikram Ravi analyzed between 60 and 69 FRBs and found that about three-quarters of the universe’s baryonic matter lies in the intergalactic medium.
  • The research quantified signal delays in bursts ranging from 12 million to more than 9 billion light-years away, using FRBs as “cosmic flashlights” to weigh diffuse gas.
  • Findings indicate that another 15% of ordinary matter resides in galaxy halos, with the remainder confined within stars and cold galactic gas.
  • Dispersion measurements confirm that thin, wispy gas spread throughout the cosmic web solves the long-standing missing baryon problem.
  • Next-generation radio arrays such as the DSA-2000 are expected to detect thousands of FRBs annually, enabling detailed mapping of the cosmic web and insights into galaxy formation processes.