Telescopes including ZTF, Catalina and Palomar tracked a months-long flare from AGN J2245+3743 — powered by a ~500-million-solar-mass black hole — that briefly emitted as much light as 10 trillion suns. Published November 4 in Nature Astronomy, the event brightened by a factor of 40 and was about 30× stronger than comparable AGN flares. Researchers ruled out a supernova and favour a tidal disruption event, noting AGN disks can feed unusually massive stars. At ~10 billion light-years away the flare is seen slowed by cosmological time dilation and remains ~2 magnitudes above its pre-flare level.
Record-Breaking Black Hole Flare Outshines 10 Trillion Suns
Telescopes including ZTF, Catalina and Palomar tracked a months-long flare from AGN J2245+3743 — powered by a ~500-million-solar-mass black hole — that briefly emitted as much light as 10 trillion suns. Published November 4 in Nature Astronomy, the event brightened by a factor of 40 and was about 30× stronger than comparable AGN flares. Researchers ruled out a supernova and favour a tidal disruption event, noting AGN disks can feed unusually massive stars. At ~10 billion light-years away the flare is seen slowed by cosmological time dilation and remains ~2 magnitudes above its pre-flare level.
23:33, 04.11.2025Science
Record-Breaking Black Hole Flare Outshines 10 Trillion Suns
Researchers using the Zwicky Transient Facility (ZTF), the Catalina Real-Time Transient Survey and Palomar Observatory instruments have recorded a months-long outburst from AGN J2245+3743 that briefly emitted as much light as 10 trillion suns. The source is powered by a supermassive black hole roughly 500 million times the mass of the Sun. At its peak the flare brightened by a factor of 40 and was about 30 times more intense than any previously recorded AGN-related flare.
The observations and analysis appear in a study published November 4 in Nature Astronomy. Caltech astronomer and ZTF project scientist Matthew Graham, a co-author on the paper, described the behaviour as unprecedented among AGNs. The team first noticed a rise in brightness on April 2, 2018, but an early spectrum from Palomar's 200-inch Hale Telescope did not reveal anything unusual. By 2023 the brightening was fading far more slowly than expected; a later spectrum from the W. M. Keck Observatory showed the source had become dramatically more luminous.
Investigators ruled out several possible causes. A supernova was dismissed because such explosions cannot supply the enormous energy involved. As co-author K.E. Saavik Ford (City University of New York) noted, converting the entire mass of the Sun to energy via E=mc^2 is comparable to the total energy the flare has released since monitoring began.
The team concluded the most plausible explanation is a tidal disruption event (TDE): a star that wandered too close to the supermassive black hole was tidally shredded and accreted, producing the extreme burst of light. TDEs that occur inside active galactic nuclei are usually hidden by the bright accretion disk, but this flare was so luminous that the disk could not conceal it. The authors suggest that stars embedded in AGN disks can grow by accreting disk material, creating unusually massive stars that produce exceptionally powerful TDEs when captured.
About 100 TDEs have been recorded to date, but very few have been observed inside visibly active galactic nuclei. The previous record-holder, ZTF20abrbeie (nicknamed Scary Barbie), observed in April 2021, was roughly 30 times weaker and likely involved a star 3–10 times the Sun's mass. Located about 10 billion light-years away, J2245+3743 is also among the most distant — and therefore oldest — such events astronomers have observed, occurring when the universe was much younger.
Because of cosmological time dilation, observers on Earth see the event slowed: as Graham explained, seven years here corresponds to about two years at the source, so the flare appears to play back at roughly quarter-speed. Even after what corresponds to two years in the AGN's frame, the source remains about two magnitudes brighter than its pre-flare level.
Why this matters: This event offers a rare window into extreme accretion physics and the interaction between massive stars and AGN disks. Long-term, wide-field surveys like ZTF are crucial for finding and characterizing such rare, powerful transients.
Astronomers will continue to monitor J2245+3743 with ground-based and space observatories to track its decline and refine models of how AGN environments can produce extraordinarily powerful tidal disruptions.