Astronomers are grappling with a complex cosmic mystery lurking in the dark heart of a distant galaxy 270 million light-years from Earth. And its resolution could revolutionize our understanding of how black holes eat matter from the entire universe.
Known as 1ES 1927+654 and located in the constellation Draco, this remote island of stars has it at its core. supermassive black hole It weighs more than a million suns—and surprisingly, it’s not very noticeable. the largest galaxies, including oursthey take such great monstrosities at their center. But this black hole has been incredibly rare: The object surprised observers with a burst of radiation so intense that it apparently wiped out the black hole’s corona, a swirling cloud of billions of degrees of plasma, for three months in 2018. It was thought that it could come from somewhere tidal disruption eventwhat happens when an unlucky star gets torn up and swallowed by a black hole after getting too close. Many research teams began to closely monitor the system, watching over the next few years as the corona reassembled and quiet conditions returned, until the black hole unleashed more surprises: exploding dramatically in radio waves and flashing with rapid pulses of x-rays.
A dizzying array of dynamical activity is unprecedented around a supermassive black hole and cannot easily be explained by a typical tidal disruption. Eileen Meyer, an astronomer at the University of Maryland, Baltimore County who led an international team in the study of the system’s radio emissions using several ground-based and space-based telescopes, recalls her initial impression of 1ES 1927+654. of a very “boring, feeble radio blob”. But as he and his colleagues watched more and more strange activity develop, he realized that “this[black hole]was strange, very strange.” In particular, his team’s observations revealed that shortly after turning on the radio waves, the black hole spewed out a pair of giant, opposing jets of plasma traveling at one-third the speed of light. This was the first time creating such planes it was seen in real time, and was a clear indicator of extreme activity closer to the black hole. Meyer presented his team’s findings last week at the 245th meeting American Astronomical Society in National Harbor, Maryland, and was the lead author an attached paper It was published on January 13 Astrophysical Journal Letters.
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If the black hole’s strange behavior wasn’t a simple act of star destruction, what was? A crucial clue could lie in the timing of the black hole’s bright x-ray pulses, revealed by work led by MIT PhD student Megan Masterson. Using data from the European Space Agency’s XMM-Newton x-ray space telescope, Masterson and his colleagues found a telling pattern in the pulses: an oscillation of the glow that has become increasingly rapid over the past two years. “The period of this oscillation changed dramatically from 2022 to 2024,” says Masterson. “In 2022 we started with an 18-minute interval, and by 2024, we were within seven minutes; so the period has basically been cut in half. This has never been seen around a supermassive black hole.’ The paper that reports the resultsWritten by Masterson, Meyer and others, it was published on the arXiv.org preprint server in January and accepted for publication in the February 13 issue. nature.
The most obvious explanation for these X-ray oscillations, the researchers say, is a clear but indirect signal from a star. something orbiting very close to the black hole. It is so close, in fact, that it is plowing through the black hole accretion disk—A maelstrom of falling matter becomes incandescent due to frictional heating as it accumulates at the foot of the gravitational monster. If this were the case, the researchers realized, each bright flare would correspond to an object forming an orbital cycle, which would jump onto it and shake up the accretion disk to emit a burst of X-rays. And the strange acceleration of the oscillations seemed to be a sign that this object’s orbit was decaying, bleeding off energy and spiraling ever closer and faster to a point of no return—the black hole. event horizon—through the emission of waves called space-time gravitational waves.
For Masterson, the next step was easy: “I calculated how long it would take that body to inhale and eat,” he says. The math told Masterson that the hypothetical object’s final dive would occur in January 2024. Then the mysterious X-ray oscillations would finally stop.
But they didn’t. XMM-Newton observations of 1ES 1927+654 in March 2024 clearly showed that the oscillations were still going strong; If it was caused by an orbiting object, for about seven minutes the black hole’s companion was a few million kilometers from the event horizon and moving at half the speed of light. No object has ever been observed so close to a black hole; why didn’t this fall? Gravity should ensure its doom, unless something other than gravity is at play, Masterson thinks. And he found a promising candidate in another unexpected field: physics white dwarfsthey are stellar bodies left behind by dying sun-like stars.
If the putative object were a smaller black hole, it would plunge headlong from the accretion disk to merge with its supermassive partner, and if it were a normal star, it would have to shrink closer to form a typical tidal wave. break event But Masterson and his team realized that if it were a low-mass white dwarf, about the size of Earth, it might be hard enough to hover precariously on the brink of annihilation for a while. Instead of succumbing to the tidal forces that crush stars, such a white dwarf would throw a small fraction of its matter into the black hole. This could compensate for orbital energy lost through gravitational waves, stopping or reversing inspiration. “It’s basically something unique to do with how a white dwarf responds to mass loss and how the physics of accretion play out,” says Masterson.
This makes sense, says Chiara Mingarelli, an astrophysicist at Yale University who was not involved in the 1ES 1927+654 study. If the hypothetical object orbiting the black hole were a white dwarf, the undead star would be in a kind of tidal limbo, where it would “start to break up a little bit,” he explains, “sending out gravitational waves (while) slowly spiraling into the black hole. instead of swallowing it whole”.
However, this model remains an educated guess at best. Its validation may come relatively soon, however, with a space-based gravitational wave detector set to launch in the 2030s: the European Space Agency. Laser Interferometer Space Antennaor LISA, should be able to detect gravitational waves emitted by a white dwarf in a state of quasi-stasis around 1ES 1927+654. And even if LISA does not find such a signature, this null result should help to unravel the mystery of what is really happening in this enigmatic system; perhaps, for example, radio photons, giant jets, and x-ray pulses will be traced back to poorly understood interactions. between the disappearance and reappearance of the black hole and its coronal plasma cloud.
Regardless, “it’s an opportunity for us to study this source right now, and hopefully LISA will find many, many more (similar cosmic systems), and then we can study them all,” Masterson says.
“I was surprised and delighted that we still have so much to understand about the dynamics of black holes, especially the physics of accretion disks,” says Mingarelli, adding that LISA’s ability to study these environments could unlock many more mysteries about supermassive black holes.
“It’s no longer just about observing the static universe,” says Meyer. “Now we’re at a point where we realize that part of the universe is very dynamic, we don’t know what’s coming. There might be something new there that hasn’t been there in the last week.’
