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Fast radio burst traced to rare cluster of interacting galaxies

Researchers have recently uncovered the origins of the farthest-known fast radio burst (FRB), tracing it back to an unusual cluster of at least seven galaxies. This discovery, which was based on observations by NASA’s Hubble Space Telescope, is a remarkable development in the field of astronomy. 

At the same time, the study presents a significant challenge to existing scientific models of fast radio burst production and their sources.

Study background 

During the summer of 2022, astronomers detected what is now known as the most powerful fast radio burst ever observed. This FRB, also the farthest known to date, has its origins dating back halfway to the Big Bang, a period when the universe was a mere 5 billion years old – significantly younger than its current age of 13.8 billion years.

The research was led by a team of astronomers from Northwestern University. The experts utilized the advanced imaging capabilities of the Hubble Space Telescope to trace the origins of this extraordinary fast radio burst, named FRB 20220610A. 

Rare phenomenon 

The findings have contradicted initial beliefs that the radio burst originated from a single galaxy. Instead, the scientists have traced its birthplace to a collection of at least seven galaxies, closely packed and possibly interacting with each other, a phenomenon that is exceedingly rare in the universe.

Study lead author Alexa Gordon, a graduate student in astronomy at Northwestern’s Weinberg College of Arts and Sciences, emphasized the critical role of Hubble’s imaging in unraveling this mystery. 

“Without the Hubble’s imaging, it would still remain a mystery as to whether this FRB originated from one monolithic galaxy or from some type of interacting system,” said Gordon. “It’s these types of environments – these weird ones – that drive us toward a better understanding of the mystery of FRBs.”

Fast radio bursts 

The study, which will be presented at the 243rd meeting of the American Astronomical Society in New Orleans, offers new insights into the nature of FRBs. These are brief, intense bursts of radio waves that emit more energy in milliseconds than our sun does in an entire year. 

The fast radio burst in question was notably four times more energetic than previously observed FRBs and has set a new record for distance.

A complex scenario 

Initially, the source of FRB 20220610A appeared as an indistinct, blob-like structure. This led to early assumptions that it originated from either a single irregular galaxy or a cluster of distant galaxies. 

However, Hubble’s sharp imagery revealed a more complex scenario – a compact group of galaxies so densely packed that they could fit within the Milky Way. This discovery has led to speculation about the galaxies possibly exchanging material or even merging.

Professor Wen-fai Fong, a co-author of the study, pointed out the rarity of such compact galaxy groups and the potential for this interaction to trigger bursts of star formation. 

“There are some signs that the group members are ‘interacting,'” Fong said. “In other words, they could be trading materials or possibly on a path to merging. These groups of galaxies (called compact groups) are incredibly rare environments in the universe and are the densest galaxy-scale structures we know of.”

Rare birthplace 

“This interaction could trigger bursts of star formation,” said Gordon. “That might indicate that the progenitor of FRB 20220610A is associated with a fairly recent population of stars which matches what we’ve learned from other FRBs.”

“Despite hundreds of FRB events discovered to date, only a fraction of those have been pinpointed to their host galaxies,” said study co-author Yuxin (Vic) Dong. “Within that small fraction, only a few came from a dense galactic environment, but none have ever been seen in such a compact group. So, its birthplace is truly rare.”

Unknown mechanisms 

In the years since astronomers first discovered fast radio bursts in 2007, up to 1,000 FRBs have been discovered. Experts generally agree that FRBs must involve a compact object, such as a black hole or neutron star, but the exact mechanisms remain a mystery.

“Radio waves, in particular, are sensitive to any intervening material along the line of sight – from the FRB location to us,” said Fong. 

“That means the waves have to travel through any cloud of material around the FRB site, through its host galaxy, across the universe and finally through the Milky Way. From a time delay in the FRB signal itself, we can measure the sum of all of these contributions.”

Future research 

Gordon noted that with technology continually becoming more sensitive, improved detections are right around the corner.

“With a larger sample of distant FRBs, we can begin to study the evolution of FRBs and their host properties by connecting them to more nearby ones and perhaps even start to identify more strange populations,” said Dong.

“In the near future, FRB experiments will increase their sensitivity, leading to an unprecedented rate in the number of FRBs detected at these distances,” said Gordon. “Astronomers will soon learn just how special the environment of this FRB was.”

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