Astronomers have identified the largest and most distant black hole flare, which originated from the supermassive black hole at the heart of the active galactic nucleus (AGN) J2245+3743, located 10 billion light-years from Earth.
The black hole was first observed in 2018 by the US National Science Foundation (ZTF)-funded Zwicky Transient Facility (ZTF) at the Palomar Observatory of the California Institute of Technology (Caltech), and by the Caltech-led Catalina Transient Real-Time Survey, also funded by the NSF.
The team’s findings, published in the journal Nature Astronomy on Tuesday, November 4, suggest that similar events may be occurring throughout the universe, waiting to be discovered.
The black hole, 500 million times the mass of the Sun, swallows a star that gets too close, triggering a tidal disturbance (TDE) as the black hole sucks in its remains.
“This is unlike any AGN we’ve seen before. The energetics show that this object is very distant and very bright,” said Matthew Graham, ZTF scientist and team leader at Caltech.
“A fish halfway down the whale’s esophagus.”
The flare intensified by a factor of 40 over several months, peaking at 30 times the brightness of any previous black hole flare, and releasing the energy equivalent of 10 trillion suns. The strongest TDE before that was “Scary Barbie” (ZTF20abrbeie).
The black hole’s glow fades, indicating that it is still devouring a star with an initial mass 30 times the mass of the Sun. In contrast, the star that is devoured in a “Scary Barbie” event has a mass between 3 and 10 times the mass of the Sun.
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As Graham describes, the persistent nature of this glow is like “a fish only halfway down the whale’s gullet.” Researchers benefit from studying this flare because the immense gravity of supermassive black holes causes time to slow down near the event horizon.
“It’s a phenomenon called cosmic time dilation due to the expansion of space and time,” Graham said. “As light travels through expanding space to reach us, its wavelength stretches as does time itself. Seven years here is two years there. We are watching the event repeat at a quarter of the speed.”
The time dilation effect highlights the value of long-term surveys such as the ZTF. The J2245+3743 flare stands out because, of the approximately 100 TDEs detected, many do not occur in active galactic nuclei due to the masking effects of black hole emission. The size of J2245+3743 made it more visible than typical TDEs associated with AGN.
Initially, the flare did not appear significantly until 2023, when Keck Observatory data confirmed its unusual energy. The team verified that this intense flare was not a supernova, making it the brightest black hole flare ever observed, indicating the presence of a TDE associated with a very massive star.
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“Supernovae are not bright enough to explain this,” KE Savic Ford, a team member and researcher at the Graduate Center at the City University of New York (CUNY), said in the statement. “Stars this massive are rare, but we think stars inside the disk of active galactic nuclei can grow larger. Matter is thrown from the disk onto the stars, causing their mass to grow.”
While they wait for data from the Vera C Rubin Observatory, which may also identify typically strong TDEs, the team will continue searching the ZTF for similar events.
(Tags for translation) Largest black hole flare
