Prepare to be amazed! Astronomers have witnessed a cosmic event of epic proportions: a black hole flare, the brightest and most distant ever recorded, erupting from a staggering 10 billion light-years away. This incredible discovery offers a glimpse into the dramatic fates that await massive stars and the supermassive black holes lurking at the centers of galaxies.
Imagine a star, perhaps one of the most colossal in the universe, meeting an unexpected and violent end. Instead of a glorious supernova, this star appears to have been torn apart by a supermassive black hole. The black hole's immense gravity shredded the star, consuming it bit by bit, and resulting in an extraordinary burst of energy.
This phenomenon is the likely explanation for a new study published in Nature Astronomy, which describes the record-breaking flare. The source of this dazzling display, initially observed in 2018 by the Zwicky Transient Facility (ZTF) and the Catalina Real-Time Transient Survey, rapidly intensified by a factor of 40 over a few months. At its peak, this flare shone with the luminosity of 10 trillion suns, making it 30 times brighter than any previous black hole flare observed.
The culprit behind this celestial spectacle is an active galactic nucleus (AGN), specifically J2245+3743. This AGN houses a supermassive black hole estimated to be 500 million times more massive than our sun. Because of the vast distance, we are observing this event as it occurred in the distant past, when the universe was young.
"The energetics show this object is very far away and very bright," explains Matthew Graham, the study's lead author and a research professor of astronomy at Caltech. "This is unlike any AGN we've ever seen."
But here's where it gets controversial... The team is still monitoring the fading flare, and they've also considered a fascinating aspect of cosmic time. Due to cosmological time dilation, time runs slower at the black hole's location compared to our own. This means that while we've been observing the event for 7 years, only 2 years have passed in the black hole's frame of reference. It's like watching a movie in slow motion!
To understand the cause of this tremendous light burst, researchers carefully considered several possibilities. The most probable explanation is a tidal disruption event (TDE). This occurs when a star ventures too close to a supermassive black hole and is torn apart by the black hole's intense gravitational forces. The continued activity of the flare suggests that the star is not yet fully consumed, a scenario Graham describes as "a fish only halfway down the whale's gullet."
If this is a TDE, the black hole likely devoured a star at least 30 times more massive than our sun. This event dwarfs the previous record holder, nicknamed "Scary Barbie," which originated from another AGN but was 30 times less intense, with a star estimated to be between 3 and 10 solar masses.
And this is the part most people miss... Most of the approximately 100 TDEs observed to date have not occurred around AGNs. AGNs, with their supermassive black holes and swirling disks of material, can mask TDE bursts, making them difficult to detect. However, the sheer magnitude of the J2245+3743 flare made it easier to spot.
Initially, J2245+3743 didn't stand out. However, in 2023, the team noticed the flare was decaying slower than expected, which led them to obtain a spectrum from the W. M. Keck Observatory in Hawai'i. This confirmed the extreme brightness of the AGN.
"At first, it was important to establish that this extreme object was truly this bright," says co-author K. E. Saavik Ford. After ruling out other possibilities, the team concluded that J2245+3743 was indeed the brightest black hole flare ever recorded.
"If you convert our entire sun to energy using Albert Einstein's famous formula E = mc², that's how much energy has been pouring out from this flare since we began observing it," Ford says.
Once the unprecedented brightness was established, the team investigated the potential causes. They ruled out supernovae and favored the scenario of a supermassive black hole slowly devouring a massive star.
"Stars this massive are rare," Ford notes, "but we think stars within the disk of an AGN can grow larger. The matter from the disk is dumped onto stars, causing them to grow in mass."
This discovery suggests that similar events are likely occurring throughout the cosmos. Researchers plan to analyze more ZTF data to find additional examples, and the Vera C. Rubin Observatory may also identify unusually large TDEs.
"We never would have found this rare event in the first place if it weren't for ZTF," Graham states. "We've been observing the sky with ZTF for seven years now, so when we see anything flare or change, we can see what it has done in the past and how it will evolve."
What are your thoughts? Do you think this is the most exciting astronomical discovery of the year? Do you find the idea of time dilation fascinating? Share your opinions in the comments below!
