It's been about two months sinceScientists have revealed to the world the first true photograph of a black hole, but astronomers have been studying these mysterious objects for more than a century. Modern research method: sophisticated computer modeling, allowing to visualize black holes with an unprecedented level of detail, which no one of the telescopes available to mankind can yet point out. Recently, an international team of scientists created the most detailed computer models of a black hole and with the help of them proved a nearly half a century riddle connected with the nature of accretion disks - matter that eventually falls into a black hole.
Simulation results conducted byAstrophysicists from universities in Amsterdam, Oxford and Northwestern University show that the internal area of the accretion disk is located in the equatorial plane of the black hole, according to a press release published on the website of Northwestern University (USA).
The half century riddle of black holes
Their discovery solves the riddle originally describeda physicist and Nobel laureate John Bardin and astrophysicist Jacob Petterson in 1975. At that time, scientists said that the vortex part of the black hole should force the inner region of the inclined accretion disk to position itself in the equatorial plane of the black hole.
This discovery reveals the riddle originallydescribed by physicist and Nobel laureate John Bardin and astrophysicist Jacob Petterson in 1975. It was then that Bardin and Petterson stated that the vortex part of the black hole should force the inner region of the inclined accretion disk to position itself in the equatorial plane of the black hole.
After decades of searching for evidence of the effectBardeen-Peterson's new modeling by an international team of researchers made it possible to determine that, although the outer region of the accretion disk remains inclined, its inner region adapts to the equatorial plane of the black hole. The team of scientists came to this by reducing the thickness of the accretion disk to an unprecedented degree and taking into account the magnetic turbulence that is responsible for the accretion of the disk. Previous models dealing with this issue were significantly simpler and simply took into account the approximate effects of turbulence.
“This is a breakthrough discovery of the Bardeen-Peterson effectsolves an issue that has been haunting astrophysicists for more than four decades, ”commented Alexander Chekovsky of Northwestern University, one of the co-authors of the study.
"These details are in close proximity to the blackthe holes may seem insignificant, but they have a profound effect on what happens inside the galaxy. These effects control how quickly the black hole will rotate and, therefore, what impact it will have on the entire galaxy. ”
"These simulations not only solve the 40-year-olda riddle, but also, contrary to the general opinion, prove that it is possible to simulate the brightest accretion disks taking into account the general theory of relativity. Thus, we have paved the way for the next generation of simulations that will allow us to solve even more important problems with bright accretion disks, ”adds study author Matthew Liska of the University of Amsterdam.
Why do we need black hole models?
Almost all of our knowledge of black holes is based onstudying their accretion disks. Without these bright gas rings, dust and other remnants of dead stars orbiting around black holes, astronomers will not be able to see black holes to study them. In addition, accretion disks control the growth and speed of rotation of black holes, so an understanding of their nature is crucial for understanding how black holes evolve and function.
From the days of Bardeen and Petersonthe simulation was too simplistic to confirm the alignment of the inner part of the disk. In computing, astronomers encountered two limitations. First, it turned out that accretion disks approach so close to a hole that they move in a curved space-time, which falls into a black hole with great speed. In addition, the rotating force of a black hole causes space-time to rotate after it. Proper consideration of both of these key effects requires Einstein’s general theory of relativity, which predicts how objects affect the geometry of space-time around them.
Secondly, at the disposal of scientists was notThere is enough computational power to account for magnetic turbulences or disturbances inside the accretion disk. These perturbations allow disk particles to stick together and keep a circular shape, ultimately allowing the disk gas to sink in a black hole.
“Imagine that you have this thin disk. Your task is to separate the turbulent flows inside the disk. It’s really a challenge, ”says Chekovsky.
Without the possibility of separating these parts, astrophysicists could not really model realistic black holes.
Black Hole Simulation
To develop computer code capableTo model inclined accretion disks around black holes, Liska and Chekovsky used graphics (GPU) instead of central processing units (CPUs). Extremely effective in creating computer graphics and image processing, graphics processors speed up the creation of images on the screen. Compared to CPUs, they are much more efficient in computing algorithms that process huge amounts of data.
Chekovsky compares a GPU with 1000 horses, and a CPU with a Ferrari with a 1000 horsepower engine.
“Imagine that you are moving to a new apartment. You will have to travel many times from your apartment to Ferrari, because it does not fit a lot of baggage. But if you could put one box on each of a thousand horses, you could have transported all the things at once. This is the power of the GPU. It has many components, each of which is individually slower than the CPU, but there are a lot of them, ”explains Chekovsky.
In addition, Liska adds, for his measurementsThey used the method of adaptive grinding of the computational grid, which uses a dynamic grid that changes and adapts to the flow of motion throughout the simulation. This method allows you to save energy and computer resources, focusing only on certain blocks of the grid, where, in fact, there are movements of flows.
Researchers point out that usingGPUs allowed to speed up the simulation, and the use of adaptive mesh - to increase the resolution of this simulation. Ultimately, scientists were able to create models of very thin accretion disks with a height-to-radius ratio of 0.03. Modeling such a thin disk, the researchers were able to see the equation of the plane of the accretion disk near the black hole.
“The thinnest modeled disks had a height of up to a radius of about 0.05, and it turned out that interesting things happen only at 0.03,” Chekovsky says.
Astronomers note that even with such thin disks, black holes still emit strong jets of particles and radiation.
"No one expected to see such thin disksable to throw jets. Everyone expected that the magnetic fields creating these streams would tear these thin disks, and yet they are still there, and thanks to that we can solve such observational riddles, ”Chekovsky says.
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