Astronomers Discover Mysterious Radio Burst from 8 Billion Years Ago In Unprecedented Finding

Scientists have discovered by far the most ancient and distant “fast radio burst,” a type of enigmatic bright radio pulse from deep space, using a sophisticated radio telescope in Australia, reports a new study. The burst, known as FRB 20220610A because it was detected on June 10, 2022, occurred about eight billion years ago, making it about two billion years older than the previous FRB record-holder. 

The unprecedented detection not only extends our view of these strange bursts further back in space and time than ever before, it could also help unlock persistent mysteries about our universe, including its expansion rate and the whereabouts of “missing” matter that may lie hidden between galaxies.

For more than a decade, astronomers have been baffled by a class of extremely short and bright flashes from deep space, known as fast radio bursts (FRBs), that have never been fully explained. First discovered in 2007, FRBs are extremely bright pulses of radio light that typically last for a fraction of a second. Some FRBs light up the skies just once, while others curiously repeat their signals, and sometimes exhibit strange periodic patterns. Scientists think these radiant cosmic flares are likely produced by neutron stars, a special type of dead star that is extremely dense and possesses strong magnetic fields, though the exact mechanisms behind the bursts is still a mystery.

Now, scientists led by Stuart Ryder, an astrophysicist at Macquarie University, report the discovery of the first FRB ever seen at “redshift 1,” a cosmological measurement that translates to an age of about eight billion years and a distance of about 10 billion light years. In order to be seen across such a huge swath of time and space, the burst must have been extraordinarily bright. Ryder and his colleagues describe the strange properties of the ancient flash and conclude that “FRB 20220610A and other high-luminosity FRBs are challenging to explain” with current physical models, according to a study published on Thursday in Science.

“Our goal has always been to try and track these fast radio bursts across as much of the universe as we possibly can, for two reasons,” Ryder told Motherboard in a call. “One is because we want to understand what causes them, and that's something we still don't really have a firm handle on. But the other reason is because they can be very useful as what we call ‘cosmological probes.’ In other words, they can tell us about other stuff in the universe, independent of what actually causes the burst itself.”

“It turns out that fast radio bursts are potentially just as powerful, and maybe more useful in the long run, in telling us about the structure of the universe” as other cosmological probes, such as supernovas, he added. “But for that to be true, we would need to be able to see them at much larger distances than we have currently been able to do.”

Scientists have spotted several dozen FRBs since 2007, and have managed to track down the origins of many bursts to galaxies located within a few billion light years of the Milky Way. But when Ryder and his colleagues first saw observations of FRB 20220610A captured by the Australian Square Kilometer Array Pathfinder (ASKAP), one of the world’s most sensitive radio arrays, they quickly realized it could have come from a much more far-fung and ancient location.

The main clue about the unprecedented nature of this burst was the unique signature of its light. As light from FRBs travels across the universe, it encounters hot gasses and particles in intergalactic space that stretch out lower-frequency wavelengths in the pulse. This pattern of stretched-out light, known as the dispersion measure, can help scientists estimate the distance and age of a burst.

After observing the high dispersion measure of FRB 20220610A, Ryder and his colleagues searched for the source of the flash using the European Southern Observatory’s Very Large Telescope. The team successfully traced the origin of the burst to a trio of close galaxies that existed eight billion years ago.

“That was pretty exciting—that we could see where the burst came from,” Ryder said. “It appears to be a merging system of galaxies. Finally, we used the spectrograph on the Very Large Telescope and measured the stretching of the optical spectrum, the so-called ‘redshift’ of the host galaxy system. We realized then that we definitely nailed the most distant fast radio burst that anyone has ever found—and not just by a small amount; this was about 50 percent more distant than our previous record-holder.”

“That was pretty exciting to make that sort of jump in space and time,” he continued. “This is the first burst that has traveled more than half the age of the universe to get to us on Earth.”

The discovery pushes the observational horizon of these strange bursts to a new frontier, enabling the team to test out theories about FRB properties at great distances. For instance, the researchers were able to validate a key prediction of their late colleague, Jean-Pierre ‘J-P’ Macquart, who pioneered research into FRBs before he passed away in 2020. 

Macquart suggested that the greater the distance to an FRB, the more diffuse gas it would reveal between galaxies, a correlation now known as the Macquart relation. Ryder and his colleagues showed that this prediction largely holds true even at the unprecedented distance of FRB 20220610A, though they note that the immediate environment around an FRB source might complicate the relation. For instance, FRB 20220610A has a higher dispersion measure than predicted by the Macquart relation, which suggests that the object that produced this burst is surrounded by a messy environment of dust and gas that left its own imprint on its light.

Ultimately, scientists hope that extremely distant bursts, like FRB 20220610A, could help to reveal the so-called “missing” normal matter in the universe. When researchers try to add up all the familiar matter in space that makes up galaxies, stars, and planets, the sum often falls short of predictions. Scientists have long suspected that the missing mass exists in the form of elusive particles, like electrons, that drift in the immense voids between galaxies. FRBs could finally illuminate these entities, which are otherwise difficult to spot.

To that end, Ryder and his colleagues plan to continue studying ASKAP’s observations of FRB 20220610A, which was so bright that it cannot be fully explained by current models. The researchers will also keep searching for other FRBs across the sky, and they hope that future telescopes, such as the enormous Square Kilometer Array, will be able to spot even more distant bursts that could help to measure mysterious properties of the universe.

“You never know what the next burst is going to tell you,” Ryder concluded. “Maybe one day there will be a Nobel Prize for whoever figures out what causes the bursts, but right now we're just going to go off and start using them [as cosmological probes] because it's fun.”


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