In a groundbreaking discovery, astronomers have pinpointed the location of the universe's missing ordinary matter. This matter, composed of atoms, was previously undetectable. The research team used fast radio bursts (FRBs), powerful flashes of radio waves from distant galaxies, to illuminate the intergalactic medium (IGM).
The 'missing' matter, also known as baryons, makes up about 5% of the universe. Scientists have long struggled to account for this matter, as it seemed to be absent from observations of stars and galaxies. The study, published in June 2025, analyzed 69 FRBs to measure how their light slowed down as it passed through the IGM.
The findings revealed that approximately 76% of the normal matter resides in the IGM, with 15% in galactic halos and 9% within galaxies. This aligns with simulations of the universe's evolution and provides a detailed census of where this matter is located. Future projects, such as the DSA-2000 radio telescope, are expected to further advance cosmological studies using FRBs.