In a groundbreaking discovery, scientists have detected a series of exceptionally strong and rapidly evolving radio signals coming from beyond the center of a distant galaxy.
The rare cosmic signals link a tidal disruption event involving a black hole’s destruction of a star, revealing that these massive astronomical objects can remain active even when separated from galactic cores by significant distances.
The discovery, made by an international team led by astronomers at the University of California, Berkeley, challenges our ideas about where supermassive black holes are found in our universe and how they behave.
The research, which also marks the first tidal disruption event (TDE) astronomers have logged that produced a bright radio emission from beyond the center of a galaxy, was supported by researchers with the Racah Institute of Physics at the Hebrew University of Jerusalem.
The unusually powerful and delayed radio signals produced by the event, dubbed AT 2024tvd, suggest the presence of processes behind how black holes eject material over long periods, which astronomers had not previously observed. Specifically, the research team behind the discovery says it marks the fastest-evolving instance involving a radio detection that has ever been associated with a TDE event.
“This is truly extraordinary,” said Dr. Itai Sfaradi, who led the research and is the first author of a new study detailing the international team’s findings.
Tidal Forces and Black Holes
Tidal disruption events occur when a stellar body gets too close to a supermassive black hole. When this occurs, the massive gravity exerted by the black hole rips the star apart as it engages in a devastating cosmic feast.
The recent observations by Sfaradi and his team mark an exceptional TDE; however, this black hole was spotted by astronomers nearly 2,600 light-years from the core of its host galaxy. This is significant, since it offers crucial evidence that supermassive black holes can lurk in some unexpected places.
Given the unprecedented nature of the discovery, at the heart of the team’s findings are the observations made possible by high-quality detections obtained by several of the world’s premier radio telescopes, which include the Arcminute Microkelvin Imager Large Array (AMI-LA) in the United Kingdom, as well as the Very Large Array (VLA) near Socorro, New Mexico.
Additional data obtained by the Atacama Large Millimeter/submillimeter Array (ALMA), as well as the ATA and SMA observatories, were also used by the team in their research.
Based on data obtained by Hebrew University researchers using the AMI-LA observations, the peculiar radio emissions generated by this TDE were revealed. These emissions formed one of the most important components in the broader discovery and offered important clues about the physics underlying the event.
A Pair of Massive Radio Flares
According to the team’s observations, data revealed a pair of distinctive radio flares that were both massive and evolved far more quickly than any observed in the past. Significantly, the data indicated that the outflow of material from the black hole coinciding with these emissions occurred several months after the death of the star in question, rather than occurring at or near the time of its destruction.
This unique observation suggested that the processes underlying stellar consumption by black holes during such TDEs are far more complex and occur over a longer period than previously expected. Additionally, models employed by the team showed that two separate ejection events occurred, each separated by several months, which suggests that black holes are able to enter periods of dormancy, after which they reawaken in the aftermath of TDEs and release additional material.
An Unprecedented Observation
“Never before have we seen such bright radio emission from a black hole tearing apart a star, away from a galaxy’s center, and evolving this fast,” Dr. Sfaradi said. “It changes how we think about black holes and their behavior.”
Professor Assaf Horesh of Hebrew University in Jerusalem called the discovery “one of the [most] fascinating discoveries I’ve been part of.” In the past, Sfaradi studied under Horesh as a graduate student, and their recent work marks the culmination of several years of investigations into such astrophysical phenomena.
“The fact that it was led by my former student, Itai, makes it even more meaningful,” Horesh said in a statement.
The team’s paper, “The First Radio-Bright Off-Nuclear TDE 2024tvd Reveals the Fastest-Evolving Double-Peaked Radio Emission,” is now available in The Astrophysical Journal Letters, and can be read on the preprint arXiv.org server.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com