Prepare to be amazed and perhaps a little baffled as we delve into a cosmic mystery that has left astronomers scratching their heads! A mind-bogglingly powerful flare, emanating from a supermassive black hole, has been spotted 10 billion light-years away. But here's where it gets controversial... this black hole seems to have devoured a star, but not in the way we'd expect!
The most massive stars are known to end their lives as brilliant supernovae, leaving behind black holes. However, this particular star, it seems, never got the chance to fulfill its destiny. In a cosmic twist, it wandered too close to a colossal black hole, which swallowed it whole, tearing it apart into tiny fragments.
This extraordinary event was described in a recent study published in Nature Astronomy, detailing the most intense and distant flare ever recorded from a supermassive black hole. The cosmic object, first observed in 2018 by the Zwicky Transient Facility and the Catalina Real-Time Transient Survey, rapidly brightened by a factor of 40 over a few months, reaching a peak luminosity 30 times greater than any previous black hole flare. At its brightest, this flare shone with the light of 10 trillion suns!
The supermassive black hole behind this spectacle, known as an active galactic nucleus (AGN), is estimated to be a whopping 500 million times more massive than our sun. It resides in the remote universe, 10 billion light-years away, which means we're observing it as it was in the past, when the universe was still young.
"The sheer brightness and distance of this object make it unique," says Matthew Graham, lead author of the study and research professor of astronomy at Caltech. "It's unlike any AGN we've encountered before."
Astronomers continue to monitor this fading flare, but time itself seems to be playing tricks on us. Due to the cosmological time dilation caused by the stretching of space and time, the event appears to be playing back at quarter speed compared to our own experience of time.
"As the light travels across the expanding universe to reach us, its wavelength stretches, and so does time itself," Graham explains.
To unravel the mystery behind this dramatic burst of light, researchers examined various possibilities, ultimately concluding that a tidal disruption event (TDE) is the most likely culprit. A TDE occurs when a supermassive black hole's gravity tears apart a star that ventures too close, slowly consuming it as it spirals into the black hole. The fact that the flare from J2245+3743 is still ongoing suggests we're witnessing a star being devoured, but not quite fully, like a fish only halfway down a whale's throat, according to Graham.
If this flare is indeed a TDE, the supermassive black hole has consumed a star with a mass at least 30 times greater than our sun. The previous record holder for the largest candidate TDE, nicknamed Scary Barbie, was significantly weaker, and its doomed star was estimated to be between three and 10 times the mass of our sun.
Most of the roughly 100 TDEs observed to date do not occur around AGN, which are massive structures consisting of supermassive black holes surrounded by large disks of material that feed the central black hole. The recent jumbo flare, J2245+3743, was so large that it stood out from the crowd.
Initially, J2245+3743 didn't seem extraordinary. In 2018, after its discovery, researchers used the Hale Telescope at Caltech's Palomar Observatory to obtain a spectrum of its light, but nothing unusual was revealed. In 2023, the team noticed that the flare was decaying slower than expected, so they obtained another spectrum from the W. M. Keck Observatory in Hawai'i, which confirmed the extreme brightness of this AGN.
"Establishing the true brightness of this object was crucial," explains K. E. Saavik Ford, a co-author and professor at the City University of New York. "It was possible that the light was beaming towards us rather than glowing in all directions, but data from NASA's WISE mission helped rule that out."
After considering and ruling out other scenarios, the researchers concluded that J2245+3743 was indeed the brightest black hole flare ever recorded.
"If you were to convert our entire sun into energy using Einstein's famous formula, E = mc2, that's the amount of energy that has been pouring out from this flare since we began observing it," Ford says.
Once the unprecedented brightness of the event was established, the team turned their attention to its cause. Supernovae, they determined, were not bright enough to account for this flare. Their favored explanation is a supermassive black hole slowly tearing apart a massive star.
"Stars of this size are rare," Ford says, "but we believe stars within the disk of an AGN can grow larger. The matter from the disk accumulates on stars, causing them to increase in mass."
Finding a black hole meal of such epic proportions suggests that similar events are likely occurring across the cosmos. The researchers hope to uncover more such events by mining through ZTF data, and the Vera C. Rubin Observatory may also discover unusually large TDEs.
"We owe this rare discovery to ZTF," Graham says. "With seven years of sky observations under our belt, we can see what objects have done in the past and how they will evolve."
This cosmic mystery leaves us with a thought-provoking question: Are we witnessing a rare event, or are such mega-proportioned black hole meals more common than we realize? What do you think? Share your thoughts in the comments!
