A black hole 10 billion light-years away suddenly ‘ignited’ and became one of the brightest ‘transient’ objects ever detected

Scientists scouring the world for signs of a rare explosion may have stumbled upon an even more remarkable find: a massive black hole that “lit up” in the early universe, changing from dim to extremely bright in the cosmic blink of an eye.

The black hole, called J221951, is estimated to be about 10 billion light-years from Earth, meaning it turned on its lights when the universe was about a quarter of its age today. Despite the vast distance, the light was so bright that astronomers initially thought it was a stellar explosion less than 1 billion light-years away.

The fact that the black hole appeared so bright from so far away makes it one of the most luminous transients, objects that brighten suddenly and then fade, ever detected, according to the authors of a study accepted for publication in the journal Monthly Notices of the Royal Astronomical Society and available as a preprint on arXiv.

“Our understanding of the different things supermassive black holes can do has expanded greatly in recent years,” said study co-author Matt Nicholl, an astronomer at Queen’s University Belfast. “J221951 is one of the most extreme examples of a black hole to surprise us.”

The first surprise came when the researchers traced the path of a gravitational wave, a fast-moving ripple in spacetime created by the most massive cosmic collisions. The team hypothesized that the wave was released during the collision of two dense, dead stars known as neutron stars, which are known to go off in bright bursts called kilonova explosions.

The ripple in space-time did indeed lead to a luminous object. But unlike a kilonova, which initially appears blue before fading to red over several days, this spot in the sky remained bright and blue for months, far longer than a stellar explosion should.

Subsequent observations with multiple telescopes, including NASA’s Hubble Space Telescope and the Neil Gehrels Swift Observatory, revealed that the mysterious object is aligned with the center of a faint and distant galaxy, suggesting it could be a supermassive black hole, like this one. at the center of the Galaxy. After 10 months of brilliance, the object finally began to fade again, proving that it was not a galaxy itself but a transient object undergoing an intense, high-energy “outburst.”

If J221951 is indeed a supermassive black hole, its sudden burst of brightness has two possible explanations, according to the researchers. First, the black hole could have pulled a star into orbit, stretching and tearing the star apart in a messy process called a tidal disruption event, or “spaghettiization.” The second, more mysterious possibility is that the black hole could be changing state from dormant to active as it suddenly began to burrow into the rapidly moving disk of gas surrounding it.

Understanding exactly why the black hole “lit up” will require further studies of the object’s energy production. If the black hole suddenly glows again, that would mean it’s probably in feeding mode, the team concluded. But if it fades for good, it’s more likely that some unlucky star was devoured in the most spectacular way imaginable. May we all burn so gloriously.