Astronomers have made an exciting discovery about ordinary matter in the universe. For years, scientists have been trying to figure out where all the normal matter—like stars and planets—exists. This matter differs from dark matter, which we can’t see but know is there because of its gravitational effects. A recent study published in Nature Astronomy used fast radio bursts (FRBs) to locate this elusive matter. Their findings shed light on cosmic structures and how galaxies evolve.
Fast radio bursts are powerful flashes of radio waves coming from far-off regions of space. Scientists are intrigued by these bursts not just for their strength but also for their ability to reveal hidden parts of the universe. By studying how the light from these bursts spreads as it travels, researchers can estimate the amount of ordinary matter in its path. “The FRBs shine through the fog of the intergalactic medium. By measuring how the light slows down, we can gauge that fog,” explained Liam Connor, an assistant professor at Harvard and the study’s lead author.
One of the most shocking findings from this research is that about 76% of all ordinary matter in the universe is found between galaxies, in the intergalactic medium. This idea challenges previous views that most of the matter was concentrated in galaxy halos or cold gas within galaxies. The study shows that only 15% of normal matter exists in these halos, while the bulk is floating freely in between galaxies. This breakthrough helps confirm models of cosmic structure based on simulations, which previously lacked observational backing.
The study analyzed 69 FRBs, some as far as 9.1 billion light-years away. This variety allows scientists to investigate both nearby and distant bursts. The farthest FRB recorded, known as FRB 20230521B, helps scientists study areas of space too faint for usual telescopes. Researchers utilized several observatories, including the Deep Synoptic Array-110 (DSA-110) and the W.M. Keck Observatory.
The way FRBs operate is a bit like casting shadows. As their radio waves pass through cosmic matter, they scatter. The more matter there is, the more the signal spreads out. This dispersion helps astronomers estimate the amount of nearly invisible matter. “It’s like seeing the shadow of all the baryons, with FRBs as the backlight,” said Vikram Ravi, an assistant professor at Caltech. Studying these “shadows” helps give a clearer picture of the hidden matter in the universe.
In addition to shaping our understanding of matter in space, these findings reflect a wider trend in astronomy: the use of innovative tools and technology to explore cosmic mysteries. As research in this area grows, we may discover even more about the fabric of our universe.
