Tracing Fast Radio Bursts
The universe is full of mysterious signals, but few are as baffling or energetic as Fast Radio Bursts (FRBs). Recently, astronomers achieved a monumental breakthrough by tracing the most distant and powerful FRB ever detected. This discovery does not just break records; it provides a critical tool for weighing the cosmos and locating the universe’s “missing” matter.
The Discovery of FRB 20220610A
On June 10, 2022, the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope in Western Australia picked up a signal that stood out from the rest. The burst, cataloged as FRB 20220610A, lasted only a fraction of a second. Despite its brief duration, it carried an immense amount of energy.
Researchers determined that in those few milliseconds, the burst released the same amount of energy that our Sun emits over 30 years. However, the true shock came when they calculated how far the signal had traveled.
Breaking the Cosmic Speed Limit
Most FRBs detected previously originated in the local universe. This specific signal was different. It came from 8 billion years ago. This means the burst occurred when the universe was less than half its current age.
To put this in perspective, the light from this explosion began its journey before the Earth even existed. The previous record-holder was around 5 billion light-years away. FRB 20220610A smashed this record, proving that these mysterious events occur much further back in cosmic history than astronomers previously confirmed.
Pinpointing the Source
Finding an FRB is difficult, but pinpointing its exact home galaxy is even harder. It requires coordination between radio telescopes that detect the flash and optical telescopes that can see the galaxies in visible light.
The Role of the VLT and Hubble
Once ASKAP localized the direction of the signal, astronomers turned to the European Southern Observatory’s Very Large Telescope (VLT) in Chile. They looked for the source galaxy at the coordinates provided by the radio data.
Initial images suggested the source was a single, amorphous galaxy. However, the data prompted further investigation using the Hubble Space Telescope. Hubble’s sharper view revealed a surprise. The source wasn’t a single lonely galaxy. Instead, the burst originated from a compact group of two or three galaxies that were in the process of merging.
This context is vital for understanding what causes FRBs. Merging galaxies are chaotic environments. They often trigger rapid star formation. This supports the leading theory that FRBs are produced by magnetars. Magnetars are highly energetic neutron stars—the crushed cores of dead massive stars—with incredibly strong magnetic fields. A galaxy merger would create the perfect conditions for birthing the massive stars that eventually collapse into magnetars.
Weighing the Universe
The significance of FRB 20220610A extends beyond its age and power. These bursts serve as cosmic scales. As the radio waves travel through space, they pass through the diffuse gas that fills the void between galaxies. This gas slows down the different frequencies within the radio burst.
By measuring the spread of arrival times between high and low frequencies—a value known as the “dispersion measure”—astronomers can calculate exactly how much matter the signal passed through.
Solving the Missing Matter Problem
Cosmologists have long faced a problem: the “missing matter” dilemma. When they calculate the amount of normal matter (baryons) that should exist based on the Big Bang, the numbers do not match what they see in stars and galaxies. About half of the normal matter seemed to be missing.
The leading theory is that this matter exists as hot, diffuse gas in the cosmic web between galaxies. It is too faint to see with optical telescopes, but it is dense enough to affect radio waves.
This relationship between the distance of an FRB and the dispersion of its signal is called the Macquart relation, named after the late Australian astronomer Jean-Pierre Macquart.
The discovery of FRB 20220610A confirms that the Macquart relation holds true even out to extreme distances of 8 billion light-years. The signal’s dispersion matched the amount of matter predicted by standard cosmology. This effectively “found” the missing matter, proving it is hiding in the intergalactic medium.
The Technology Behind the Trace
This discovery was a triumph of international hardware and collaboration.
- ASKAP (Australian Square Kilometre Array Pathfinder): Located at the Murchison Radio-astronomy Observatory, this array of 36 dish antennas works together to scan the sky rapidly. Its wide field of view is essential for catching transient events like FRBs.
- VLT (Very Large Telescope): Operated by the ESO in the Atacama Desert, this optical telescope provided the redshift data needed to determine the distance (redshift 1.01).
- Keck Observatory: Located in Hawaii, the Keck telescopes also contributed data to confirm the redshift and distance of the host galaxy group.
Why This Matters for Future Science
Dr. Stuart Ryder from Macquarie University and Dr. Ryan Shannon from Swinburne University of Technology led this research. Their findings suggest that FRBs are common enough and bright enough to be used as tools to map the structure of the universe.
If astronomers can detect FRBs from even further back—perhaps 10 billion years or more—they can map how matter was distributed in the early universe. This helps refine our understanding of how the cosmos evolved from a uniform soup of particles into the complex web of galaxies we see today.
Current and future telescopes, such as the Square Kilometre Array (SKA) currently under construction in Australia and South Africa, will likely detect thousands of these bursts. Each one will act as a pinprick of light, illuminating the invisible structure of the dark universe.
Frequently Asked Questions
What exactly is a Fast Radio Burst? A Fast Radio Burst (FRB) is a transient radio pulse of high energy that lasts only a few milliseconds to a few seconds. They are extremely bright in the radio spectrum but invisible to the human eye.
Did this signal come from aliens? No. While the exact mechanism is still being studied, the evidence overwhelmingly points to natural astrophysical phenomena. The leading candidates are magnetars (highly magnetized neutron stars) created during stellar explosions or galaxy mergers.
Why is the “dispersion measure” important? The dispersion measure tells scientists how much “stuff” the radio wave hit on its way to Earth. This allows astronomers to calculate the density of the universe and locate matter that is otherwise invisible to optical telescopes.
How much energy did FRB 20220610A release? In less than a second, this burst released the equivalent energy of what our Sun produces in 30 years. It is the most energetic FRB ever observed.
What is the Macquart relation? The Macquart relation is a formula that correlates the distance of an FRB with its dispersion measure. It effectively states that the further away a burst is, the more intergalactic gas it passes through. This relation allows astronomers to use FRBs to weigh the universe’s baryonic matter.