Astronomers have been left baffled by a cosmic discovery that defies longstanding theories about how stars interact with supermassive black holes. A powerful flare, linked to a star being torn apart by a black hole, was observed twice—two years apart—by a team of researchers led by Tel Aviv University. This phenomenon challenges current understandings of tidal disruption events and raises intriguing questions about the true nature of these cataclysmic occurrences. The findings were published in The Astrophysical Journal Letters.
A Cosmic Surprise: Two Flares, Two Years Apart
At the center of every large galaxy lies a supermassive black hole, each one capable of wreaking unimaginable havoc on the stars that venture too close. These black holes, which can be millions to billions of times the mass of the sun, are known to pull stars into a destructive embrace. When a star approaches a black hole too closely, it can get torn apart in a process known as a tidal disruption event. During this event, material from the star is pulled into the black hole, and what remains is expelled into space, emitting a burst of energy visible across vast cosmic distances.
The flare observed by astronomers in 2022, AT 2022dbl, was thought to be a typical example of this kind of event. However, the surprise came when a nearly identical flare was detected in the same region of space, coming from the same black hole, just two years later. This marks the first confirmed case of a star surviving an initial encounter with a black hole and returning for a second, nearly identical flare.
Rethinking the Nature of Tidal Disruption Events
This discovery is groundbreaking because it challenges the widely accepted idea that a star is completely destroyed in a tidal disruption event. Previously, astronomers believed that such events resulted in the total annihilation of the star, with no possibility of survival. The observation of a similar flare originating from the same black hole years later suggests that the star might have only been partially disrupted during the first event, with part of it surviving and returning for a second encounter.
“The question now is whether we’ll see a third flare after two more years, in early 2026,” says Prof. Iair Arcavi, one of the lead researchers on the study. “If we see a third flare,” continues Arcavi, “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.”
This revelation forces astronomers to rethink their understanding of these spectacular flares. If the second flare was also the result of a partial disruption, it could imply that all such events previously believed to be full stellar disruptions might actually be a more complex process.
A Shifting Perspective on Supermassive Black Holes
The study was led by Dr. Lydia Makrygianni, who is currently at Lancaster University in the UK, under the guidance of Prof. Arcavi from Tel Aviv University. The researchers suggest that this discovery opens up a new avenue for understanding the role of supermassive black holes in the evolution of galaxies. These black holes, which are found at the centers of most large galaxies, play a crucial role in shaping their environments. The study challenges previous assumptions that these black holes only have the power to completely destroy stars. Instead, the new findings indicate that the process might involve a complex cycle of partial destruction and regeneration.
“The second flare could have been the full disruption of the star,” explains Prof. Arcavi. “The implication is that partial and full disruptions look almost identical, a prediction made before this discovery by the research group of Prof. Tsvi Piran at the Hebrew University.” If this hypothesis is correct, it would fundamentally change how astronomers interpret tidal disruption events and the information they provide about black holes. “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.”
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