Star Survives Black Hole: A Cosmic Return
A Black Hole’s Second Helping: Repeated Flare Challenges Understanding of Stellar Disruption Events
Astronomers have witnessed a rare event - a supermassive black hole flaring up twice from the disruption of a single star.This unexpected repetition is forcing scientists to rethink long-held assumptions about how black holes consume stellar material and could unlock new insights into the enigmatic giants at the heart of galaxies.
The initial flare, designated AT 2022dbl, was observed in 2022. Typically,when a star wanders too close to a supermassive black hole,the immense gravitational forces tear it apart in a ”tidal disruption event” (TDE).This violent process creates a brilliant flare of radiation as the stellar debris is heated and swallowed by the black hole. However, the brightness and temperature of AT 2022dbl were surprisingly low, puzzling astronomers.
Now,two years later,the same black hole has flared up again,almost identically to the first event. This remarkable recurrence suggests the initial flare wasn’t the result of a complete stellar destruction, but rather a “partial disruption” – a cosmic snack rather than a full meal. Much of the star survived its first encounter and, against all expectations, returned for a second pass.
“The question now is weather we’ll see a third flare after two more years, in early 2026,” says Professor Iair Arcavi of Tel Aviv University, who led the international research team. “If we see a third flare, it means that the second one was also the partial disruption of the star. So maybe all such flares, which we have been trying to understand for a decade now as full stellar disruptions, are not what we thought.”
The research, published in The Astrophysical Journal Letters, was conducted by a team including Dr. Lydia Makrygianni (Lancaster University, UK), Professor Ehud Nakar (Tel aviv University), and students Sara faris and Yael Dgany, alongside collaborators from around the globe.
supermassive black holes reside at the center of most, if not all, large galaxies, including our own Milky Way – the subject of the 2020 Nobel Prize in Physics. Despite their prevalence, much remains unknown about their formation and influence on their host galaxies. Black holes themselves are invisible, making them difficult to study directly. Astronomers typically infer their presence by observing the movement of stars in their vicinity, but this is challenging in distant galaxies.
Tidal disruption events offer a unique opportunity to ”illuminate” these otherwise hidden behemoths. When a star is ripped apart, the resulting debris forms a swirling disk around the black hole, heated to unbelievable temperatures and radiating brightly across the electromagnetic spectrum. this provides a brief window for astronomers to study the black hole’s properties.
Though, the observed characteristics of these flares have consistently defied theoretical predictions. The AT 2022dbl event may finally provide the key to resolving this discrepancy.If the second flare represents another partial disruption, it suggests that partial and full disruptions can appear remarkably similar – a prediction previously made by the research group of Professor Tsvi Piran at the Hebrew University.
“Either way,” Arcavi concludes, ”we’ll have to re-write our interpretation of these flares and what they can teach us about the monsters lying in the centers of galaxies.” The continued observation of AT 2022dbl promises to revolutionize our understanding of these powerful cosmic events and the supermassive black holes that drive them.