Scientists Locate Universe’s Long-Missing Ordinary Matter

In June 2025, scientists announced they have located the “missing” half of the universe’s ordinary matter using data from 69 fast radio bursts (FRBs), resolving a decades-old cosmic mystery.

Key Points

The Mystery of Missing Matter: While ordinary (baryonic) matter makes up only 15% of all matter in the universe, about half of it had remained unaccounted for—until now.
Where It Was Hiding: The missing matter was found primarily as wispy plasma in the intergalactic medium—thin, ionized gas stretching between galaxies.
Detection Method: Researchers used FRBs—powerful radio pulses likely from magnetized neutron stars—whose signals were dispersed by the matter they passed through, allowing scientists to map this otherwise invisible gas.
Data Sources: The study analyzed 69 FRBs, 39 of which were detected by Caltech’s Deep Synoptic Array of 110 telescopes, with distances up to 9.1 billion light-years from Earth.
Distribution of Ordinary Matter: 76% lies in intergalactic space, 15% in halos around galaxies, and just 9% within galaxies as stars and gas.
Scientific Impact: The discovery helps complete the baryon census of the universe and opens the door to deeper exploration of dark matter, which remains elusive despite dominating the universe’s mass.