This black hole's flare burned 10 trillion times brighter than the sun

A supermassive black hole tearing apart a star has set a new record for creating the brightest and most distant flare, shining with the light of 10 trillion suns at its peak. 

The flare came from an active black hole at the center of a galaxy some 10 billion light-years away in space. Called J2245+3743, the outburst's light began reaching Earth in 2018, when the Zwicky Transient Facility in California and the Catalina Real-Time Transient Survey in Arizona first detected it. Over just a few months, the flare’s brightness increased by a factor of 40, making it 30 times stronger than any previous black hole flare observed.

The black hole is roughly 500 million times more massive than the sun. Astronomers believe the flare is the result of a so-called tidal disruption event, when a star ventures too close and is torn apart by a black hole’s gravity. In this case, the doomed star is also enormous — at least 30 times more massive than the sun. As its gas spirals inward like water circling a drain, the black hole consumes it, releasing an unfathomable burst of energy.

That the flare is ongoing suggests the black hole hasn't finished its meal yet, said Matthew Graham, a Caltech astronomy professor and first author of the study, likening the star's situation to "a fish only halfway down the whale's gullet" in a statement.

A paper describing the discovered superflare appears in the journal Nature Astronomy.

Black holes are some of the oddest curiosities in the cosmos. They are regions where gravity is so strong that nothing, not even light, can escape. About a half-century ago, astronomers weren't even sure they were real. Today, black holes aren't just accepted science, they're getting glamor shots. The Event Horizon Telescope achieved the first image of a black hole, located 53 million light-years away in the Messier 87 galaxy, in 2019.

A black hole generates a flare when gas, dust, or, in this case, a star gets too close and gravity rips it apart. As the material falls inward, it gets hotter, glowing brightly before disappearing. 

Most events of this kind have been observed happening around quiet black holes. But this one is an active galactic nucleus, meaning it has already been feeding on surrounding gas. That perpetual glow has the potential to mask flares, but the immense power of this event made it easier to detect.

The previous record holder, ZTF20abrbeie, is estimated to have come from a star just three to 10 times the mass of the sun. 

Follow-up observations confirmed the flare’s brightness. Data from NASA’s WISE mission helped eliminate other possible explanations, such as supernovas or a cosmic optical illusion known as gravitational lensing. The flare appeared in visible and infrared light but not in X-rays, radio waves, or neutrinos, ghostly particles that pass through almost everything without interacting, ruling out other types of explosions.

Still, the idea that the doomed star was 30 times more massive than the sun made this interpretation of the data a little hard to believe. 

The Zwicky Transient Facility team installs the wide-field camera at the prime focus of the 48-inch Samuel Oschin Telescope at Palomar Observatory in California. Credit: Caltech Optical Observatories

"Stars this massive are rare," said coauthor K. E. Saavik Ford, a CUNY professor, in a statement, "but we think stars within the disk of an (active galactic nucleus) can grow larger. The matter from the disk is dumped onto stars, causing them to grow in mass."

Because the galaxy lies so far away, astronomers are seeing the event as it happened long ago, when the universe was less than a third of its current age. The flare is still fading, slowed by the effects of cosmic expansion, which stretches both space and time.

Researchers say the finding hints that many more supersized flares may be awaiting discovery as next-generation sky surveys, including the Vera C. Rubin Observatory, come online.