Astronomers have recently observed a star, designated AT 2022dbl, that survived a close encounter with a supermassive black hole not once, but twice. This groundbreaking discovery challenges previous understandings of tidal disruption events (TDEs), where stars are typically expected to be completely torn apart when they get too close to a black hole.
Tidal Disruption Events (TDEs)
A tidal disruption event (TDE) occurs when a star ventures too close to a supermassive black hole. The immense gravitational forces from the black hole stretch and distort the star, a process dramatically known as "spaghettification" 🍝. This stretching force, called a tidal force, overwhelms the star's own gravity, causing it to be ripped apart.
Normally, the shredded stellar material forms an accretion disk around the black hole, heats up to extreme temperatures, and emits a powerful burst of radiation (a flare) that astronomers can detect across vast cosmic distances. This flare typically fades over several months or years as the material is gradually consumed by the black hole.
The Resilience of AT 2022dbl
The star AT 2022dbl is unique because it exhibited two distinct flares from the same location in space, separated by approximately 700 days. This strongly suggests that the star was not fully destroyed in its first encounter, but rather partially disrupted, losing some of its mass before escaping the black hole's immediate grasp and returning for a second "bite."
This observation overturns decades of astrophysics that largely assumed stars were completely consumed in such events. The recurring flares indicate that stars can survive these encounters, orbiting the black hole and experiencing repeated partial disruptions.
Future Implications
Astronomers are now eagerly anticipating a third flare from AT 2022dbl, expected in early 2026. If a third flare occurs, it would further solidify the hypothesis of partial disruption and offer unprecedented insights into the mechanics of these events. If it doesn't, it could imply the second encounter was fatal, but the similarity of the flares would still suggest that partial and full disruptions can look alike in their emitted light.
This discovery holds significant implications for understanding:
Black Hole Physics: It provides new ways to study the interaction between stars and supermassive black holes, potentially explaining why some TDE flares appear dimmer or cooler than predicted by older models.
Stellar Evolution: It opens up a new class of "cosmic survival stories" for stars, revealing how they might endure such violent encounters.
Galaxy Evolution: Since supermassive black holes influence the evolution of their host galaxies, a deeper understanding of their feeding habits provides crucial clues about the broader cosmic landscape.
The case of AT 2022dbl reshapes our understanding of these dramatic cosmic events and highlights the dynamic and often surprising nature of the universe.