Many years ago, scientists estimated that only 5% of the universe is composed of ordinary matter, leaving a significant portion unaccounted for. However, a recent study conducted by astronomers from the Center for Astrophysics Harvard & Smithsonian (CfA) and the California Institute of Technology (Caltech) has finally located the missing matter.

According to the researchers, over 75% of ordinary matter, known as baryonic matter, exists in the form of hot, low-density gas that resides between galaxies. This groundbreaking discovery has provided the first comprehensive measurements of how ordinary matter is distributed throughout the universe.

In a statement from CfA, astronomer Liam Connor explained that the long-standing 'missing baryon problem' was never about the existence of matter, but rather its whereabouts. Thanks to fast radio bursts (FRBs), scientists now know that the majority of ordinary matter floats in the cosmic web between galaxies.

Baryonic matter consists of protons and neutrons, but is commonly used to describe all matter made of atoms, excluding dark matter and dark energy. The researchers noted that a small fraction of baryons can be found in stars and the interstellar medium within galaxies, with the interstellar medium referring to the space between star systems.

Previous studies suggested that a significant amount of baryonic matter was dispersed throughout the intergalactic medium, the space between galaxies. However, due to the challenges in measuring this diffuse ionized gas, scientists were unable to confirm its existence or location.

By utilizing FRBs, which are rapid, bright radio signals originating from distant galaxies, the research team was able to determine that approximately 76% of all baryonic matter exists in the intergalactic medium, with 15% in galaxy halos and a small fraction in stars or cold galactic gas. This study offers direct evidence supporting cosmological simulations that predicted this distribution and provides insights into the movement of matter across the universe.

Lead author of the study, Liam Connor, highlighted the role of supermassive black holes and exploding stars in regulating the distribution of baryons, acting as a cosmic thermostat to maintain balance. Co-author Vikram Ravi from Caltech emphasized that FRBs offer a unique opportunity to uncover the invisible matter that fills the vast spaces between galaxies, leading to a new understanding of the universe's composition.

As astronomers anticipate the discovery of thousands of FRBs with advanced telescopes, the potential for unraveling more cosmic mysteries continues to grow.