For many years, scientists noticed a problem with their calculations about the universe. When they counted all the normal matter, like protons and neutrons that form stars and planets, the numbers did not add up. Most of this matter seemed to be missing.
Now, a research team has discovered where this hidden material is. They used fast radio bursts (FRBs), which are powerful flashes of radio energy from distant galaxies that last only milliseconds. As these signals travel through space, they pass through thin clouds of gas.
This journey changes the signals. Shorter, blue wavelengths pass through easily, while longer, red wavelengths are slowed down slightly by the gas. By measuring this small delay, astronomers can figure out how much invisible gas the signal traveled through.
Researchers from the Massachusetts Institute of Technology studied 2,870 FRBs detected by a Canadian telescope called CHIME. They compared this data with a map of millions of galaxies created by a tool in Arizona.
The results showed that the missing matter was not near galaxies but spread out in large, thin clouds extending millions of light-years into space. This is much farther than scientists expected.
This discovery suggests that galaxies are not isolated. Instead, they release material into space through events like exploding stars. The new map indicates that about 15 percent of the universe's normal matter is in these clouds outside galaxies, and 75 percent is in the large spaces between galaxies. Scientists now understand where the universe's missing matter has been hiding.