Cosmic Space

Scientists say we were caught in a black hole’s bull’s-eye

Nine months ago, astronomers observed a flash that they said came from a mysterious object that seemed to flare with the brilliance of a quadrillion suns, located 8.5 billion light-years from Earth.

Now they say they’ve figured out what that object was.

In a pair of studies published by Nature and Nature Astronomy, researchers report that the event was probably sparked when a supermassive black hole suddenly consumed a nearby star. The event’s violent energy was released in the form of a relativistic jet of blazing-hot material that headed in Earth’s direction.

The jet didn’t do us any damage. But its bull’s-eye directionality produced a phenomenon called “Doppler boosting,” also known as the headlight effect. That made the jet’s flash look brighter than it would have if the jet went in a different direction.

Scientists say the flash, which was designated AT2022cmc when it was detected by the Zwicky Transient Facility in February, is only the fourth known example of a Doppler-boosted tidal disruption event.

Infographic: How a disruptive black hole event sparks radiation emissions in multiple wavelengths
This graphic shows how a relativistic jet sent out from a tidal disruption event is associated with a variety of energetic emissions. (R. Hurt / Caltech / IPAC / ZTF)

“The last time scientists discovered one of these jets was well over a decade ago,” Michael Coughlin, an astronomer at the University of Minnesota Twin Cities and one of the Nature paper’s principal authors, said in a news release. “From the data we have, we can estimate that relativistic jets are launched in only 1% of these destructive events, making AT2022cmc an extremely rare occurrence. In fact, the luminous flash from the event is among the brightest ever observed.”

Soon after AT2022cmc was detected, the ZTF team put out the word for other astronomers to observe the afterglow from the flash in multiple wavelengths. Readings from observatories including the Hubble Space Telescope, the Very Large Array in New Mexico and the European Southern Observatory’s Very Large Telescope in Chile pinpointed the flash’s location on the night sky and its distance.

“This particular event was 100 times more powerful than the most powerful gamma-ray burst afterglow,” MIT astronomer Dheeraj “DJ” Pasham, the Nature Astronomy study’s principal author, said in a news release. “It was something extraordinary.”

MIT researcher Matteo Lucchini, one of Pasham’s co-authors, used the observations to create a computer model for the jet’s behavior. “We found that the jet speed is 99.99 percent the speed of light,” he said.

The physics behind the event still isn’t completely understood. Pasham said the black hole must have been in a “hyper-feeding frenzy” when the jet was launched, and the team behind the Nature study said a black hole would probably have to be spinning rapidly to rev up a jet as luminous as AT2022cmc.

As more powerful telescopes such as NASA’s James Webb Space Telescope and the Vera C. Rubin Observatory come into their prime, it’s likely that many more tidal disruption events will be detected.

“Astronomy is changing rapidly,” said University of Maryland astronomer Igor Andreoni, another principal author of the Nature paper. “More optical and infrared all-sky surveys are now active or will soon come online. Scientists can use AT2022cmc as a model for what to look for and find more disruptive events from distant black holes. This means that more than ever, big-data mining is an important tool to advance our knowledge of the universe.”

Andreoni and Coughlin head up a list of 81 authors of the Nature study, “A Very Luminous Jet From the Disruption of a Star by a Massive Black Hole.” Pasham leads a list of 66 authors of the study published by Nature Astronomy, “Disruption of a Star by a Cosmological Black Hole.”

By Alan Boyle

Mastermind of Cosmic Log, contributor to GeekWire and Universe Today, author of "The Case for Pluto: How a Little Planet Made a Big Difference," past president of the Council for the Advancement of Science Writing.

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