‘Unlike any we’ve ever seen’: astronomers detect largest, most distant black hole flare ever

The team’s findings, released in the journal Nature Astronomy on Tuesday, November 4, suggest that similar occurrences may be taking place throughout the universe, just waiting to be discovered.

The black hole, which is 500 million times the mass of the sun, is consuming a star that ventured too close, leading to a tidal disruption event (TDE) as its remains are absorbed by the black hole.

“This is unlike any AGN we’ve ever seen. The energetics show this object is very far away and very bright,” said Matthew Graham, a ZTF scientist and team leader at Caltech.

‘A fish only halfway down the whale’s gullet’

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 energy equivalent to 10 trillion suns. The strongest TDE before this was “Scary Barbie” (ZTF20abrbeie).

This black hole flare is fading, indicating that it is still consuming a star with an initial mass of 30 times that of the sun. In contrast, the star being devoured in the “Scary Barbie” event has 3 to 10 times the mass of the sun.

As Graham describes, this flare’s ongoing nature is likened to “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 run slower near the event horizon.

“It’s a phenomenon called cosmological time dilation due to the stretching of space and time. As the light travels across expanding space to reach us, its wavelength stretches as does time itself. Seven years here is two years there. We are watching the event play back at quarter speed,” said Graham.

This time dilation effect highlights the value of long-term surveys like ZTF. The J2245+3743 flare stands out because, among roughly 100 detected TDEs, many do not occur in AGNs due to the masking effects of black hole emissions. The size of J2245+3743 made it more noticeable than typical AGN-related TDEs.

Initially, the flare did not appear significant until 2023, when data from the Keck Observatory confirmed its extraordinary energy. The team verified that this extreme flare was not a supernova, establishing it as the brightest black hole flare ever observed, indicative of a TDE linked to a very massive star.

“Supernovas are not bright enough to account for this. 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,” K E Saavik Ford, team member and City University of New York (CUNY) Graduate Center researcher, said in the statement.

While they wait for data from the Vera C Rubin Observatory, which may also identify typically powerful TDEs, the team will keep searching ZTF for comparable occurrences.

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