A supermassive black hole in the process of destroying a huge star
Caltech/R. Painful (IPAC)
Astronomers have spotted the brightest flash we've ever seen coming from a supermassive black hole. The flash was so powerful that it could only have come from a huge star that was torn apart in the center of a distant galaxy in the so-called tidal disruption event (TDE), releasing an extraordinary surge of energy that has not yet completely died down.
The outbreak originated from active galactic nucleus (AGN) is a supermassive black hole at the center of a galaxy that is actively consuming matter – almost 20 billion light-years away, making it one of the most distant TDEs ever discovered. In fact, we haven't detected many of these tidal disturbances in AGNs at all because internal brightness variations near active black holes make it difficult to determine whether the flare is a TDE or something else.
“We've known what AGN are for about 60 years, and we knew they were very variable, but we didn't understand that variability,” says Matthew Graham at the California Institute of Technology. “We now have millions of AGNs and we still don't understand the variability.” Nicknamed “Superman” for its incredible brightness and power, the event could help demystify these space objects.
Superman was first spotted in 2018, but without being able to measure his distance from Earth, astronomers assumed it was simply a bright, but not unexpected, blip from a relatively nearby galaxy. It wasn't until 2023 that follow-up observations revealed that the flare was much further away, making its internal brightness much higher than researchers originally thought.
The initial flare increased the brightness of the AGN by more than 40 times, making it 30 times more powerful than the previous strongest flare ever observed from an AGN. Graham and his colleagues found that the most likely cause was massive star being torn apart: one at least 30 times the mass of the Sun, but possibly much larger.
In the region around every active supermassive black hole there is a ring of material in the process of falling, called accretion disk. The density of material in this region should form huge stars, but we have never seen them directly. “If our interpretation is correct that this is a TDE, then this proves the existence of these massive stars in the environment we suspected,” Graham says.
“We used to think that an active supermassive black hole would just have a disk of gas and it would sit there and bubble. But this is a much brighter, more dynamic environment,” he says. Studying Superman, who continues to disappear, could help us gain a deeper understanding of this medium.
It could also allow us to build a model of TDE in AGN, which we could use to find more. “Oftentimes if we see that a TDE is in one of these AGN hosts, we don't actually know whether it's just an active galactic nucleus or whether we actually have a TDE, so it's really great to have something that isn't ambiguous in that sense,” says Vivien Baldassare at Washington State University. “This will be really important for finding future TDEs and disentangling the different sources of AGN variability.”
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