Where did the universe's missing ordinary matter go?

Space · Published 11 October 2026 Swipe more like this →

In short: For decades, a cosmic discrepancy has haunted physicists: the amount of visible matter in stars and galaxies is far lower than the amount of matter that existed shortly after the Big Bang. New research suggests the missing pieces are hiding in plain sight, scattered in diffuse clouds between galaxies.

The universe presents a profound accounting problem. Following the Big Bang, scientists estimate that roughly 17 percent of all matter was composed of baryonic matter—the protons and neutrons that form the mass of atoms. However, the amount of this ordinary matter we can actually observe within stars and galaxies today is significantly less than that early-universe estimate. While the remaining 83 percent of the universe's matter is believed to be invisible dark matter, the whereabouts of the 'missing' baryonic portion has remained a mystery.

A team from the CHIME/FRB Collaboration, led by MIT researchers, has developed a way to track this elusive matter using fast radio bursts (FRBs). These are ultrabright, millisecond-long flashes of radio waves from the distant universe. As these signals travel toward Earth, they pass through cosmic structures. The more matter the signal encounters, the more the radio waves are 'smeared' or stretched in time.

By analyzing the degree of smearing in thousands of FRB signals and comparing them to known galaxy locations, researchers Haochen Wang and Kiyoshi Masui discovered that this missing matter exists in diffuse, puffy clouds surrounding galaxy groups. Crucially, these clouds extend much further than previous models predicted. This suggests that energetic processes—such as black hole jets and exploding stars—are far more violent than previously thought, capable of flinging matter out of galaxies and into the vast intergalactic void.

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