Astronomers Find Missing Matter Hiding in Plain Sight

New study reveals the universe’s “missing” ordinary matter is scattered between galaxies.

For years, scientists puzzled over a cosmic mystery: where was a significant portion of the universe’s ordinary matter? Now, a groundbreaking study reveals that more than 75% of this missing matter resides in the space between galaxies, offering a major breakthrough in our understanding of the cosmos.

Unveiling the Invisible Gas

Astronomers from the **Harvard and Smithsonian Astrophysics Center (CFA)** and **Caltech** have successfully located a substantial amount of the universe’s common matter. This ordinary matter, composed of protons and neutrons and known as baryonic matter, has been elusive. Using signals from deep space, they created a detailed map, showing this matter dispersed as an almost invisible gas between galaxies.

The team analyzed rapid radio bursts (FRBs), pulses that travel vast cosmic distances. By examining how these signals slow down, they could detect the matter they traversed. The findings suggest that most baryonic matter is dispersed throughout the intergalactic environment, an extensive area between galaxies.

“The ‘disappeared barion problem’, which dates back decades, was never trying whether the matter existed or not. It was always about: Where is? Now, due to frb, we know it: three quarters of it float between galaxies in the cosmic network,”

—Liam Connor, Astronomer of the CFA and main author of the study

This discovery aligns with computer simulations predicting a universe full of faint gas. Notably, the European Space Agency’s Euclid mission, launched in July 2023, is mapping the large-scale structure of the universe, which could confirm these findings with further precision. A 2024 study estimated that 12% of the universe’s mass is in the form of baryonic matter, the remaining is dark matter and dark energy (ESA).

The FRB Breakthrough

The research team examined 60 FRBs, originating from galaxies that are between 12 million and over 9 billion light-years away. One, FRB 20230521B, came from the farthest reaches of the cosmos. These signals act like “cosmic flashlights,” interacting with gas along their path, which causes a measurable slowdown.

The precision of this analysis was achieved because the signals could be traced back to their galaxies of origin. The findings reveal that about 76% of the baryonic matter is found within the intergalactic environment. Furthermore, approximately 15% is in gas halos surrounding galaxies, with a smaller percentage in stars or internal cold gas.

Implications and Future Research

This research gives insight on how the large-scale structure of the universe is constructed and evolved. The team believes the findings also help clarify how energy emitted from stars and black holes redistributes matter. The results provide a new understanding of how galaxies and the intergalactic medium interact, opening doors for future research.