The captured star has had many close encounters with supermassive black holes in distant galaxies, and may even have survived material tearing apart by the enormous gravitational tidal forces.
destruction of star by the gravity of supermassive black hole This is a violent event known as a Tidal Destruction Event (TDE). The gas is ripped from the star and undergoes “spaghettification”. It is shredded in the process and stretched by hot streams of matter that flow around the star. Black Hole, forming a temporary and very bright accretion disk.From our point of view, the center galaxy It looks like a flare housing a supermassive black hole.
On September 8, 2018, the Automated All Sky Survey of Supernovae (ASASSN) discovered a flare in the core of a distant galaxy 893 million light years away. The flare, cataloged as AT2018fyk, had all the characteristics of a TDE. Various X-ray telescopes including NASA Quick,European XMM-Newton, Nicer Equipment aboard the International Space Station, and Germany’s Erosita, observed the black hole to brighten dramatically. TDEs typically show a smooth decline in brightness over several years, but when the astronomer saw AT2018fyk again about 600 days after it was first noticed, the X-rays had quickly disappeared. Even more puzzlingly, about 600 days later, the black hole suddenly flared up again. what was going on?
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“Until now, it was assumed that the aftermath of a close encounter between a star and a supermassive black hole would be fatal for the star, that is, the star would be completely destroyed,” said Thomas Wevers. said. Astronomer at the European Southern Observatory and author of a new study on the event, statement“But unlike all other TDEs we know of, when we repointed the telescope at the same spot years later, we found it brightened again.”
A team of astronomers led by Wevers found that repeated flares were characteristic of stars that survived a TDE, completed another orbit, and experienced a second TDE. To fully explain what they were observing, Wevers’ group developed a model of “iterative partial TDE”.
In their model, Star was a former member of binary system You got too close to the black hole at the center of the galaxy. The black hole’s gravity blew away one of the stars, turning it into a runaway. hypervelocity star You are racing at speeds of 600 miles (1,000 kilometers) per second outside the galaxy. Another star has become firmly harnessed by a black hole in his 1,200-day elliptical orbit, which scientists call the tidal radius. Black Hole.
Because the star wasn’t fully within the tidal radius, only a portion of its material was stripped away, leaving a dense stellar core that continues its orbit around the black hole. By the time astronomers saw system flares, the star was safe near the farthest point in its orbit, because it takes about 600 days for material pulled out of the star by a black hole to form an accretion disk.
About 1,200 days after the first collision, however, as the stellar core began to approach the black hole again, the star began to recapture some of its material from the accretion disk, causing a sudden attenuation of X-ray emissions. “When the core returns to the black hole, gravitational pull essentially all the gas away from the black hole. As a result, there is no more matter to accumulate and the system darkens.” Researcher and astrophysicist at MIT It also said in a statement.
but the black hole gravity Return the favor quickly and steal more matter with the star’s approach. As with the first encounter, he explained that there was a 600-day lag between the black hole eclipsing the star and the formation of the accretion disk, and why it turned on again when the X-ray flare occurred. I’m here.
From the star’s orbit, Wevers’ team calculated that the black hole is about 80 million times more massive than the Sun, or about 20 times the mass of the black hole at the center of the Sun. milky way galaxy, Sagittarius A*.
Wevers’ team doesn’t have to wait long to see if the theory is correct. Scientists predict that AT2018fyk will fade again in August and he will brighten again in March 2025 as the core of the star returns and new material begins to accrete into the black hole.
However, there is one potential problem with the amount of mass the star has lost to the black hole. The amount of mass lost depends in part on the rotation speed of the star, which the black hole can influence. If the star is spinning fast enough to break apart, the black hole steals matter more easily, increasing mass loss.
“If the mass loss is only at the 1% level, the star is expected to survive many more encounters, but if it’s closer to 10%, the star may already be destroyed,” co-author Eric said. Coughlin said. In his statement, he referred to research from Syracuse University in New York.
In any case, TDEs and partial TDE iterations provide a valuable opportunity to know the lifetimes of supermassive black holes that are normally undetectable because they are dormant. This is important for measuring the mass of black holes and determining how they have evolved. Therefore, we can learn how the galaxies around the black hole have evolved in the history of the universe.
The findings were presented at the 241st Annual Meeting of the American Astronomical Society, Astrophysics Journal Letterboth on January 12th.
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