Astronomers detect fastest radio signals from black hole shredding star outside galaxy center

Astronomers have spotted something that shouldn't exist—or at least, something they've never seen before. A black hole, sitting roughly 2,600 light-years away from the center of its galaxy, tore a star to shreds. And as it did, the event blazed across radio frequencies with a brightness and speed that has no precedent in the scientific record.

The discovery, catalogued as AT 2024tvd, marks the first time researchers have detected a tidal disruption event—the technical term for a star being ripped apart by a black hole's gravity—producing significant radio emission from anywhere other than a galactic core. An international team led by Dr. Itai Sfaradi and Prof. Raffaella Margutti at UC Berkeley published the findings in The Astrophysical Journal Letters, with crucial contributions from researchers worldwide, including Prof. Assaf Horesh at the Hebrew University of Jerusalem's Racah Institute of Physics.

What makes this event extraordinary is not just its location, but its behavior. The radio signals evolved faster than any comparable phenomenon ever recorded. Two distinct radio flares emerged from the disruption site, each changing character at a pace that defied existing models of how these cosmic catastrophes unfold. "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," Sfaradi said. "It changes how we think about black holes and their behavior."

The observation was only possible because of a coordinated effort across some of the world's most sensitive radio telescopes. The Very Large Array, ALMA, the Arcminute Microkelvin Imager Large Array in the UK, the SMA, and the ATA all contributed data to piece together what was happening. The AMI observations, directed by Horesh's team at Hebrew University, proved especially vital in capturing the unusually rapid shifts in the radio signal—the signature detail that revealed something fundamentally different about this event.

Tidal disruption events themselves are not new to astronomy. When a star wanders too close to a supermassive black hole, the gravitational pull becomes so extreme that the star is torn apart, its material heated to billions of degrees as it spirals inward. But this event suggested something more complex was occurring. The data indicated that powerful outflows of material were launched from near the black hole not in the immediate aftermath of the star's destruction, but months later. This delay, and the violence of the outflows themselves, point to processes in the black hole's vicinity that are far more intricate than previously understood.

The location of the black hole itself challenges long-held assumptions. Supermassive black holes are thought to reside at the hearts of galaxies, anchoring them gravitationally. Finding one operating 2,600 light-years from the galactic center suggests that black holes can exist in far more varied environments than current models account for. It raises questions about how such objects form, migrate, or remain in isolation from their host galaxies.

For Horesh, the discovery carries particular resonance. Sfaradi was once his graduate student, and now leads research that places their shared institution at the center of a finding that will reshape how astrophysicists think about black hole behavior. "The fact that it was led by my former student, Itai, makes it even more meaningful," Horesh reflected. "It's another scientific achievement that places Israel at the forefront of international astrophysics." The work stands as a reminder that the universe still holds surprises—phenomena that exist outside the boundaries of where we expected to find them, behaving in ways we did not anticipate.