A Signal From 10 Billion Years Ago: The Most Distant Fast Radio Burst Ever Traced

On March 4, 2024, a pulse of radio energy swept across a field of 64 white dishes in the dry Karoo region of South Africa. It lasted a few thousandths of a second. Nobody heard it, nobody saw it, and the only sign it ever happened was a spike in a stream of computer data. But that blip had been traveling toward Earth for roughly 10 billion years, since a time before our Sun and planet even existed.

This week, an international team of astronomers announced that the signal, now known as FRB 20240304B, is the most distant fast radio burst ever traced back to the galaxy it came from. The study, led by Manisha Caleb of the University of Sydney, was published in the journal Science under a title that says it plainly: “A fast radio burst at redshift 2, three billion years after the Big Bang.”

Caleb described the timescale as “insane,” even for astronomers, in an interview with ABC News in Australia. It is hard to argue with her. And the strangest part is that, nearly two decades after the first one was found, scientists still cannot say for sure what makes these flashes.

What Is a Fast Radio Burst?

A fast radio burst, or FRB, is exactly what it sounds like: an extremely bright, extremely brief pulse of radio waves from deep space. Most last only milliseconds. Almost all come from outside our own Milky Way galaxy. Because they are radio waves, the human eye can never see them.

They are also powerful beyond easy comparison. Caleb told ABC that in those few milliseconds, a fast radio burst can release as much energy as our Sun puts out over several days. Sky & Telescope reported that this particular burst released more energy than the Sun emits in a year. Either way, it is a staggering amount of power squeezed into a flash shorter than a blink.

The first FRB was discovered by accident in 2007 in archival data from the Parkes radio telescope in New South Wales, Australia. For years afterward, some astronomers wondered whether the signals were even real or just interference from equipment on Earth. In one famous case, a set of mysterious signals at Parkes turned out to come from a microwave oven in the observatory’s kitchen being opened too early. The true bursts survived that skepticism. Telescopes around the world have since recorded thousands of them, and Caleb estimates that thousands occur across the sky every single day.

Detecting a burst is one thing. Pinning it to a specific galaxy is much harder, and that is what makes this result stand out. Only about 100 fast radio bursts have host galaxies with measured distances, and most of those are relatively close by cosmic standards.

How the Team Tracked It Down

The burst was caught by MeerTRAP, a project that searches MeerKAT’s data in real time for brief radio flashes. The team is led by Professor Ben Stappers at the University of Manchester’s Jodrell Bank Centre for Astrophysics. MeerKAT is an array of 64 dishes, each 13.5 meters across, and its sensitivity allowed the team to pin the burst’s position in the sky, southeast of the bright star Denebola in the constellation Leo.

Then the trail went cold. According to Sky & Telescope, there was no galaxy visible at that spot in existing images. Follow-up looks with the Keck Telescope in Hawaii and the MMT Observatory in Arizona found nothing either.

So the team went to the most powerful space telescope ever built. Using director’s discretionary time on the James Webb Space Telescope, they pointed Webb’s Near-Infrared Camera at the location and found a faint smudge: a dwarf galaxy so dim it registered around 28th magnitude, far beyond the reach of ordinary telescopes. Webb’s spectrograph then measured its redshift at 2.15, which places the burst roughly 10 to 11 billion years in the past.

One clue told the team early on that this burst was unusually far away. As radio waves travel through the thin gas between galaxies, lower frequencies get delayed slightly more than higher ones. Astronomers call that delay the dispersion measure, and it works as a rough distance gauge. Caleb told ABC that typical bursts register a few hundred units, maybe around a thousand. This one came in at roughly 2,400.

A Record That Doubles the Old One

Before this discovery, the record for the most distant localized fast radio burst belonged to FRB 20220610A, found by Australia’s ASKAP telescope and reported in 2023. Its light had traveled about 8 billion years. FRB 20240304B’s host lies beyond redshift 2, more than double the redshift of the next-farthest known burst, according to 404 Media’s summary of the paper.

That timing puts the burst in an era astronomers call “cosmic noon,” when galaxies across the universe were forming stars at their fastest pace. The researchers noted that the burst lets them probe ionized gas across roughly 80 percent of cosmic history.

In the paper, Caleb and colleagues note that “only a small number of FRB host galaxies have been identified” at these distances, and with good reason. Most bursts that far away are simply too faint for current telescopes to catch. This one was bright enough, and MeerKAT was sensitive enough, to cross the line.

The Galaxy That Should Not Have Been There

Here is where the story turns from record-setting to genuinely strange.

Most fast radio bursts that have been traced to a home galaxy come from big, massive galaxies that are busy forming stars. This one did not. According to the University of Oxford, which contributed to the study, the host galaxy was about 1,000 times less massive than the team expected.

“The host sticks out in the whole galaxy sample that we have. And it was not what we were expecting,” Stappers said. Caleb described it as “a little dwarf galaxy, although it was actively forming stars.”

The galaxy appears to be clumpy, low in heavy elements, and going through an intense burst of star formation. Based on its star formation rate, most of its stars may have formed within about 30 million years, a cosmic eye blink.

That detail matters because it points toward what may have caused the burst.

So What Made It? The Magnetar Theory

The leading explanation for fast radio bursts is a magnetar. A magnetar is a type of neutron star, the ultra-dense core left behind when a massive star explodes as a supernova. What sets magnetars apart is their magnetic field, which is the strongest known in the universe, roughly a thousand trillion times stronger than Earth’s. When the crust of a magnetar shifts or cracks in what astronomers call a starquake, it can release enormous bursts of energy.

A galaxy full of brand-new, massive stars should also be full of fresh supernova remnants, and therefore young neutron stars. That makes this dwarf galaxy a natural magnetar factory. “Our work suggests that it’s very unlikely that this FRB was produced by a merger,” Caleb said, referring to the alternative idea that bursts come from two neutron stars colliding. A young magnetar fits the evidence better.

Not every expert is ready to close the case. Ryan Shannon of Swinburne University of Technology, who was not involved in the study, told ABC that a magnetar is a strong candidate, pointing out that a magnetar inside our own galaxy has produced a pulse resembling a fast radio burst. But he said he would not rule out the possibility that more than one mechanism produces these flashes.

That is an honest place to be. Science does not have the final answer yet, and good scientists say so.

No, It Is Not Aliens

Any time a mysterious signal arrives from deep space, someone asks the obvious question. It is a fair one, especially in a year when the Pentagon has been releasing batches of its UFO files to the public.

But nothing about fast radio bursts points to intelligence. They are scattered randomly across the sky, they come from all kinds of galaxies, and their energy and behavior match natural processes involving collapsed stars. A signal that left its source 10 billion years ago also predates Earth itself by billions of years. The more scientists learn, the more these bursts look like the universe’s version of a lightning strike: violent, natural, and not yet fully understood.

The real mystery is not who sent the signal. It is what kind of cosmic engine can pack that much power into a few milliseconds, and why some galaxies seem to produce them while others do not.

Why It Matters

The practical payoff of this discovery may be bigger than the record itself.

Most of the ordinary matter in the universe, the stuff made of atoms, is not in stars or planets. It is spread out as thin, hot gas between galaxies, in a vast structure scientists call the cosmic web. That gas is almost impossible to see directly. Fast radio bursts offer a workaround. Every burst that travels across the universe gets slowed by that gas on the way, so measuring thousands of bursts at known distances could let astronomers weigh and map matter they otherwise cannot detect.

Shannon told ABC this would allow studies that were previously impossible. Kaustubh Rajwade of the University of Oxford, who led the software work that made the localization possible, said “MeerKAT is uniquely placed to find FRBs at such distances,” and the team expects it may catch and pin down several more far-off bursts each year.

Earlier this month, a Nobel Prize went to the scientist who turned Antarctic ice into a telescope for ghost particles. This week, a few milliseconds of radio static became a window into the young universe. The common thread is patience: building better instruments, then listening carefully for what the cosmos has been trying to tell us all along.