Astronomers are grappling with complex cosmic mysteries that lie at the heart of distant galaxies some 270 million light-years from Earth. And that resolution could revolutionize our understanding of how black holes feed on matter throughout the universe.
This remote stellar island, known as 1ES 1927+654 and located in the constellation Draco, houses a supermassive black hole at its center that weighs more than a million suns, but surprisingly… is not that noteworthy. Most large galaxies, including our own, have giant monsters like this at their centers. But this black hole turned out to be very strange. For three months in 2018, the object shocked observers with sudden bursts of radiation so intense that it apparently obliterated the black hole’s corona, a swirling cloud of billion-degree plasma. It was thought that it could have come from the tidal disruption phenomenon that occurs when an unlucky star gets too close to the ocean and is torn apart and swallowed. black hole. Numerous research groups began to closely monitor the system, until the black hole unleashed further surprises, such as dramatically flaring up in radio waves and flickering with fast pulses of X-rays, until the corona reassembled back to its quiescent state. I observed it for several years after that.
Such a dizzying combination of dynamic activity is unprecedented around a supermassive black hole and cannot be easily explained by typical tidal disruption phenomena. Eileen Meyer, an astronomer at the University of Maryland, Baltimore County, who led an international team in investigating the system’s radio emissions using multiple telescopes on the ground and in space, had her first impressions of 1ES 1927+654: I am reminiscing about it. It was very much like a “boring, faint mass of radio waves.” But as she and her colleagues saw more and more strange activity unfolding, she realized that “this[black hole]is strange, very strange.” In particular, her team’s observations revealed that shortly after the radio burst, the black hole spewed out a pair of gigantic, opposing jets of plasma that traveled at one-third the speed of light. This was the first time such jet formation had been witnessed in real time, and was a clear indication of extreme activity close to the black hole. Meyer presented his team’s findings last week at the 245th meeting of the American Astronomical Society in National Harbor, Maryland, and was the lead author of an accompanying paper published in the journal Jan. 13. Astrophysics Journal Letter.
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If not some run-of-the-mill stellar destruction, what was behind black holes’ strange behavior? A key clue may lie in the timing of black holes’ flashing X-ray pulses. That’s according to a study led by Megan Masterson, a doctoral candidate at the Massachusetts Institute of Technology. Using data from the European Space Agency’s XMM Newtonian X-ray Space Telescope, Masterson and her colleagues found a clear pattern of pulses, oscillations that blinked faster and faster over two years. . “The period of this oscillation changed dramatically from 2022 to 2024,” Masterson said. “We started with a period of 18 minutes in 2022, and in 2024 we went to a period of 7 minutes. So the period has essentially been cut in half. The paper reporting the results, co-authored by Masterson, Meyer and colleagues, was submitted to the preprint server arXiv.org in January and accepted for publication in the February 13 issue. . nature.
According to the researchers, the most obvious explanation for these X-ray oscillations is that they are clear but indirect signals of significant effects. something It orbits very close to the black hole. In fact, it’s so close that it must have penetrated the black hole’s accretion disk. The maelstrom of accreted material becomes white-hot due to frictional heating as it piles up around the gravity monster’s mouth. If so, each flickering eruption would correspond to the object completing one orbital period during which it would plummet, stirring up the accretion disk and firing off bursts of X-rays. , the researchers noticed. And the strange acceleration of the oscillations, through the emission of space-time ripples called gravity, causes this object’s trajectory to decay, draining its energy, and pushing it further and further toward the point of no return, the black hole’s event horizon. It appeared to be a sign that the waves were approaching fast.
For Masterson, the next step was easy. “I calculated how long it would take to inspire that body to eat,” she says. Mathematically, Masterson predicted that the hypothetical object’s final plunge would occur in January 2024. Then, the mysterious X-ray oscillations finally stop.
But they didn’t. XMM Newtonian observations of 1ES 1927+654 in March 2024 clearly showed that the oscillations remain strong. If caused by an orbiting object, its period of about seven minutes means that the black hole’s companion star is within millions of miles of the event horizon and traveling at half the speed of light. No object has ever been observed this close to a black hole. Why didn’t this fall? Masterson remembers thinking that unless something other than gravity was at play here, gravity should have ensured its doom. And she found one promising candidate in another unexpected field. This is the physics of white dwarfs. White dwarfs are compact stellar remains left behind by dying Sun-like stars.
If the putative object were a smaller black hole, it would have crashed headlong through the accretion disk and merged with the supermassive star. And if it were a normal star, it would have shattered on approach to cause the typical tides. chaotic event. But Masterson and his team believe that if it were a low-mass white dwarf star, about the size of Earth, it would be durable enough to temporarily remain unstable and on the brink of destruction. I realized that there is a possibility that Rather than succumb to the tidal forces tearing the star apart, such a white dwarf would drip a small portion of its material into the black hole. This could offset the orbital energy lost to gravitational waves, potentially stopping or reversing intake. “Essentially, this is something special that has to do with how white dwarfs respond to loss of mass, and how accretion physics affects it,” Masterson says.
This makes sense, says Chiara Mingarelli, an astrophysicist at Yale University who was not involved in either of the 1ES 1927+654 studies. If the hypothetical object orbiting a black hole were a white dwarf, the undead star would be on the edge of some kind of tidal current, where it would be “starting to be torn apart bit by bit,” she explains. Rather than being swallowed whole, it slowly spirals into the black hole. ”
Nevertheless, this model is at best an educated guess. But verification could come relatively soon with a space-based gravitational wave detector, the European Space Agency’s Laser Interferometer Space Antenna (LISA), scheduled to launch in the 2030s. This should be able to detect gravitational waves falling from white stars. A dwarf in quasi-stasis around 1ES 1927+654. And even if LISA doesn’t find any such signs, its invalid results should help solve the mystery of what’s really going on with this mysterious system. Perhaps, for example, radio flares, giant jets, and X-ray pulses can all be traced back to poorly understood interactions. Between a black hole and a cloud of coronal plasma that repeatedly disappears and reappears.
In any case, “This is an opportunity for us to study this one source now. Hopefully LISA will discover many more sources (similar space systems) and then we will be able to study them all. “It allows us to do research,” Masterson said.
“I was surprised and pleased that there is still so much to understand about black hole dynamics, especially the physics of accretion disks,” Mingarelli said, adding that LISA’s potential to study these environments will help improve the ability of supermassive black holes. He added that more mysteries may be unraveled.
“We’re no longer just looking at a static universe,” Meyer said. “We’re now at the point where we understand that much of the universe is very dynamic. We don’t know what’s going to happen. There might be something new that wasn’t there last week.”
