For three decades, scientists have been searching for half of the “normal” matter predicted to exist in the universe. A new study published in Nature claims to have finally located this missing matter using fast radio bursts (FRBs). This discovery resolves a long-standing discrepancy between theoretical predictions and observational data, providing a more complete understanding of the universe’s composition.
This “missing matter” refers to baryonic matter, the ordinary matter that makes up everything we can see and touch, from stars and planets to everyday objects. Unlike dark matter, which remains elusive, baryonic matter is composed of protons and neutrons. While theoretical models suggest baryonic matter constitutes 4-5% of the universe’s total mass, previous observations could only account for about half of this predicted amount.
The new research pinpoints the missing matter within the vast, sparsely populated intergalactic space. Although its existence in this region was theorized, detecting it proved challenging due to its extremely low density, equivalent to just a few atoms in an average-sized office. Traditional telescopes struggled to detect such diffuse matter.
Illustration of a fast radio burst (FRB) traveling from its host galaxy to Earth.Illustration of an FRB’s journey from its host galaxy to Earth. Image: (ICRAR)
Fast Radio Bursts: A Key to Unlocking the Mystery
The breakthrough came through the study of FRBs, powerful millisecond-long bursts of radio waves originating from distant galaxies. While their precise cause remains unknown, FRBs offer a unique tool for probing the universe. The Australian Square Kilometer Array Pathfinder (ASKAP) radio telescope, situated 800 km north of Perth, has enabled scientists to pinpoint the origin of these bursts with unprecedented accuracy, allowing them to measure the distance they travel to Earth.
Graphical representation of how FRBs were used to detect missing matter.Graphical representation of how FRBs were used to detect the missing matter. Image: (ICRAR)
Measuring the Missing Matter
By analyzing several FRBs, researchers measured the subtle “pushback” these bursts experienced as they traversed intergalactic space. Although the density of baryonic matter is low in these regions, the vast distances traveled by FRBs mean they inevitably encounter free electrons, a telltale sign of baryonic matter. These encounters cause a dispersion effect, with different wavelengths of the FRB being slowed down by varying amounts.
This dispersion allowed the team to calculate the density of electrons along the path of each FRB, providing a measure of the total baryonic matter present. Remarkably, only six FRBs were needed to estimate the baryonic content across the entire universe, with the measured density aligning closely with theoretical predictions.
Confirming Previous Findings
The new findings corroborate a 2018 study that also claimed to have accounted for the missing matter by analyzing primordial light from the early universe. Both studies point to the intergalactic medium as the reservoir for this previously undetected baryonic matter. Independent verification of these results will further strengthen the conclusions.
Implications for Our Understanding of the Universe
Locating the missing baryonic matter is a significant step forward in our understanding of the universe’s composition and evolution. This matter plays a crucial role in shaping the cosmic web, the framework within which galaxies, stars, and planets form. The discovery provides a more complete picture of the universe and lays the groundwork for future research into the intricate processes that govern its structure and evolution.
This groundbreaking research, leveraging the unique properties of FRBs, has solved a decades-old mystery and deepened our understanding of the universe’s composition. The ability to pinpoint the origin of FRBs and analyze their dispersion has proven to be a powerful tool for probing the vast intergalactic spaces and revealing the secrets of the missing baryonic matter.
