Astronomers have observed the most powerful flare ever detected originating from a supermassive black hole, an event believed to be caused by the dramatic disruption of a massive star. This extraordinary burst of energy, dubbed “Superman” due to its incredible brightness, provides a rare opportunity to study the dynamic environment surrounding these cosmic giants and offers clues to understanding black hole variability.
The Phenomenon: A Tidal Disruption Event (TDE)
The flare emerged from an active galactic nucleus (AGN), a supermassive black hole located at the center of a galaxy actively consuming matter. Situated nearly 20 billion light years away, this marks one of the most distant TDEs ever detected. A tidal disruption event occurs when a star gets too close to a black hole’s immense gravitational pull. The black hole’s gravity stretches and tears the star apart in a process called spaghettification, releasing a tremendous amount of energy.
Difficulty in Detection: AGNs and Variability
Detecting these events in AGNs is challenging because the inherent brightness fluctuations around active black holes make it difficult to distinguish between a TDE and other sources of variability. “We’ve known what AGNs are for about 60 years, and we knew that they were very variable, but we didn’t understand the variability,” explains Matthew Graham at the California Institute of Technology. Despite observing millions of AGNs, the underlying cause of their variability remains a mystery. The unprecedented brightness of “Superman” offers a potential breakthrough in understanding these cosmic objects.
Unmasking “Superman”: A Delayed Discovery
Initially spotted in 2018, the flare was initially assumed to originate from a relatively close galaxy, as astronomers were unable to measure its distance from Earth. It wasn’t until 2023, with follow-up observations, that the flare’s vast distance was revealed, confirming its extraordinarily high intrinsic brightness – far greater than initially estimated. The flare increased the AGN’s brightness by over a factor of 40, significantly outshining the previous strongest flare ever recorded from an AGN by a factor of 30.
The Culprit: A Stellar Giant
The most likely cause of this spectacular event, according to Graham and his colleagues, is the disruption of a truly massive star. They estimate the star’s mass to be at least 30 times that of our sun, and possibly much larger.
Stellar Nurseries Around Black Holes
Around every active supermassive black hole exists a ring of material spiraling inwards, known as an accretion disc. The intense conditions within this disc are thought to foster the formation of massive stars, though direct observation of these stars has been elusive. “If our interpretation is correct that this is a TDE, then it is proving the existence of these massive stars in that environment, which we have suspected,” says Graham. The discovery supports the idea that supermassive black holes are not just “burbling along” but exist in vibrant, dynamic environments.
Future Research and Implications
Studying “Superman” as it gradually fades promises to provide deeper insights into the environment surrounding supermassive black holes. It may also enable astronomers to develop models for identifying TDEs in AGNs, facilitating the discovery of more events. “Often if we see that a TDE appears to be in one of these AGN hosts, we don’t really know if this is just the active galactic nucleus acting up or if we really have a TDE, so it’s really great to have something that’s not ambiguous in that way,” states Vivienne Baldassare at Washington State University. This discovery is an important step in unraveling the sources of variability in AGNs and expanding our understanding of these powerful cosmic phenomena.
The details of this research are published in The Astrophysical Journal Letters (DOI: 10.3847/2041-8213/ae0b5e).
