It’s not often that a black hole outshines 10 trillion suns, but when it does, the universe notices-and so do the astronomers. The most luminous black hole flare ever recorded has burst from the active galactic nucleus J2245+3743, a supermassive black hole about 10 billion light-years away, releasing an energy output unparalleled in observational history. Detected in 2018 with the Zwicky Transient Facility, the flare brightened by a factor of 40 within just months and reached its peak luminosity 30 times greater than ever seen from any flare stemming from a black hole.
This cosmic spectacle is the work of a tidal disruption event: a star strayed too close to a black hole, getting torn apart in the process, the victim of overwhelming gravitational forces. In this case, however, the doomed star was extraordinary, at least 30 times the mass of the Sun, far larger than the stars usually involved in known TDEs. For comparison, the previous record holder, a star with three to ten solar masses dubbed “Scary Barbie,” was 30 times less luminous. “This is unlike any AGN we’ve ever seen. The energetics show this object is very far away and very bright.”
The supermassive black hole at the centre of J2245+3743 is estimated to have a mass of 500 million solar masses and is enveloped in a thick accretion disk of gas and dust. Though AGNs are intrinsically variable due to their feeding activity, the scale and persistence of this flare have been unusual. “If you convert our entire Sun to energy, using Albert Einstein’s famous formula E = mc^2, that’s how much energy has been pouring out from this flare since we began observing it,” said K. E. Saavik Ford of the City University of New York.
One reason astronomers can study the flare in such detail is because of cosmological time dilation relativistic effect in which time appears to run more slowly in regions of strong gravity and over great cosmic distances. As Graham said, Seven years here is two years there. We are watching the event play back at quarter speed. This time-stretching, confirmed in recent studies of variability in distant quasars, lets researchers trace the flare’s evolution with unprecedented clarity, capturing the star’s gradual demise as if in slow motion.
Detection within an AGN is extremely rare, as a TDE’s transient light often gets buried under a constant emission coming from the accretion disk. This flare managed to break through the normal variation seen in this particular AGN. Follow-up spectroscopy at the W. M. Keck Observatory in 2023 showed the flare to be extremely bright; data from NASA’s retired Wide-field Infrared Survey Explorer ruled out directional beaming and a supernova as possible explanations.
The mechanics of the disruption involve the star crossing the black hole’s tidal radius-the point at which gravitational forces exceed the star’s self-gravity. Hydrodynamical simulations show that as the star is stretched into a stream of gas, roughly half of its material becomes bound to the black hole, forming a temporary accretion structure that radiates intensely in optical, ultraviolet, and X-ray wavelengths. In AGN environments, such interactions can also feed existing stars within the disk, potentially explaining how such massive stars form in the first place. As Ford observed, “Stars this massive are rare, 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.”
The detection underscores the importance of wide-field surveys like ZTF, which scan large portions of the sky repeatedly to catch rare, short-lived phenomena. Because ZTF maintains a seven-year archive of observations, astronomers can reconstruct an event’s history and distinguish unusual flares from the routine variability of AGNs. Future facilities such as the Vera C. Rubin Observatory should be able to significantly extend this capability and perhaps discover even more extreme TDEs, further refining models of star-black hole interactions.
J2245+3743 represents something rare for astrophysicists: a laboratory to explore both tidal disruption physics and the dynamics of AGN disks. Because the flare is still fading years after its peak, the longevity of the flare provides a prolonged window into how supermassive black holes consume stellar material. Graham frames this as “a fish only halfway down the whale’s gullet,” a cosmic meal in process, revealing the secrets to some of the Universe’s most energetic environments.
