What does it take to outshine 10 trillion suns? In the case of the cosmic flare nicknamed “Superman,” the answer is a supermassive black hole tearing apart one of the largest stars ever found near a galactic centre. Astronomers have confirmed that this outburst, detected 10 billion light-years away, is the most luminous and distant flare ever observed from a black hole; it is rewriting the physics of extreme galactic environments.
The source, known as J2245+3743, is an active galactic nucleus, or AGN, a compact, intensely bright region powered by a black hole weighing around 500 million solar masses. In AGNs, gas and dust spiral into an accretion disk, heating to millions of degrees and radiating across the electromagnetic spectrum. But this flare was far beyond the usual feeding glow. Over months, it brightened by a factor of 40, peaking at 30 times the luminosity of any previous black hole flare. At its maximum, it radiated the energy output of the Sun converted entirely into electromagnetic radiation, as K. E. Saavik Ford explained: “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.”
The most compelling explanation is a tidal disruption event, where a star comes too close to a black hole and gets torn apart by tidal forces. Half of the stellar debris is then flung outward, while the rest spirals inward, forming a bright accretion stream. In this case, the doomed star was at least 30 solar masses largest ever seen destroyed in such an event. By comparison, the previous record holder, ZTF20abrbeie “Scary Barbie”, involved a star only three to ten times the Sun’s mass and was 30 times less luminous.
It is unusual to detect such a flare within an AGN. The dense, bright environment of an accretion disk normally obscures other transients, which is why most of the ~100 known TDEs are more easily detectable in “quiet” galaxies. In this case, the event’s incredible scale cut through the AGN’s own brilliance. It was first mistakenly identified as a blazar, but the flare’s true nature was only uncovered after years of monitoring from wide-field surveys such as the Catalina Real-Time Transient Survey and the Zwicky Transient Facility (ZTF), designed to catch transient cosmic events. Follow-up spectroscopy with the W. M. Keck Observatory unveiled the extreme luminosity, and archival data from NASA’s retired Wide-field Infrared Survey Explorer excluded directional beaming toward Earth.
Another clue is the persistence of the flare. From the Earth’s frame of reference, it has been fading for seven years, but due to cosmological time dilation-the stretching of space and time as light travels across the expanding universe-only two years have passed at the place where the flare occurred. “Seven years here is two years there. We are watching the event play back at quarter speed,” says Matthew Graham at Caltech. And because we are seeing the event in slow replay, astronomers can study the physics of stellar shredding in unprecedented detail.
Events like “Superman” belong to the emerging class of Extreme Nuclear Transients, which are smooth, long-lived, and at least twice as energetic as any other known transient. ENTs can reach peak luminosities of 2 × 10⁴⁵ to 7 × 10⁴⁵ erg/s, roughly 100 times more than typical Type Ia supernovae and remain bright for hundreds of days in their own frame. Their rarity is staggering: estimated rates are about 10,000 times lower than superluminous supernovae at similar cosmic epochs. The disruption of such a massive star in proximity to a black hole suggests unusual stellar populations in AGN disks. As Ford summarised, material from the disk can be accreted onto stars, enabling them to grow to well above typical masses before they meet their demise.
This process supplies not only the fuel for extreme flares but also provides a means for the rapid growth of black holes in the early universe, when galactic centres were denser and more chaotic. Future surveys, including Vera C. Rubin Observatory’s Legacy Survey of Space and Time and NASA’s Roman Space Telescope, are poised to detect similar events at even larger distances, out to redshifts of 4-6. Each detection will probe both the high-mass end of the stellar initial mass function and the upper limits of black hole feeding physics. For now, “Superman” stands as the brightest beacon ever recorded from a black hole, a cosmic laboratory where gravity, radiation, and stellar matter collide on scales that challenge the limits of astrophysical theory.
