It took about two months from the moment scientists showed the world the first real picture of a black hole, but the study of these mysterious objects astronomers have been doing for more than a century. The modern method of research: a complex computer simulation that allows to visualize black holes with unprecedented level of detail, to note that while neither one of mankind’s telescopes. Recently, an international team of scientists has created the most detailed computer model of a black hole and using them has proved almost half a century of mystery associated with the nature of accretion disks of matter that falls into a black hole.
The results of the simulations carried out by astrophysicists from the universities of Amsterdam, Oxford, and northwestern University, show that the inner region of the accretion disk located in the Equatorial plane of the black hole, according to a press release published on the website of northwestern University (USA).
Half-century mystery of black holes
Their discovery solves the mystery, originally described by physicist and Nobel laureate John Bardeen and astrophysicist by Jacobus Petersham in 1975. At the time scientists said that the vortex of the black hole should force the inner region of the accretion disk inclined to position themselves in the Equatorial plane of the black hole.
This discovery reveals the mystery, originally described by physicist and Nobel laureate John Bardeen and astrophysicist by Jacobus Petersham in 1975. That’s when Bardeen and Petterson said that the vortex of the black hole should force the inner region of the accretion disk inclined to position themselves in the Equatorial plane of the black hole.
After decades searching for evidence of the effect of the Bardeen-Peterson a new simulation of an international team of researchers allowed us to determine that, although the outer region of the accretion disk remains tilted, its inner region is adapted to the Equatorial plane of the black hole. A team of scientists has come to this, reducing the thickness of the accretion disk to an unprecedented degree, and having taken into account the magnetic turbulence responsible for accretion disk. Previous models dealing with this question was much simpler and just took into account the estimated effects of turbulence.
“This is a breakthrough discovery effect Bardeen-Peterson tackles the question that haunts astrophysicists for more than four decades,” says Alexander Chakovski from northwestern University, one of the authors of the study.
“These details are in the vicinity of a black hole may seem insignificant, but they have a profound effect on what is happening inside the galaxy. These effects control how fast to spin the black hole and therefore what impact it would have on the entire galaxy”.
“These simulations not only solve 40-year mystery but, contrary to General opinion, prove that it is possible to simulate the bright accretion disks taking into account the General theory of relativity. Thus, we paved the way for the next generation of simulations that will enable us to solve even more important problems with bright accretion disks,” adds the study’s lead author Matthew Liska from the University of Amsterdam.
Why do we need models of black holes?
Almost all our knowledge of black holes is based on the study of their accretion disks. Without these bright rings of gas, dust, and other remnants of dead stars rotating around black holes, astronomers cannot see black holes to study them. In addition, accretion disks controls the growth and the speed of rotation of black holes, so understanding their nature is crucial to understanding how black holes evolyutsioniruet and function.
Since Bardeen and Peterson to the present day simulation was too simple to confirm the alignment of the inner part of the disk. In calculations, the astronomers were faced with two constraints. First, it turned out that the accretion disks are approaching so close to the hole that we are moving in a curved space-time, which with great speed falling into a black hole. In addition, the rotating force of a black hole causes space-time to rotate behind her. Proper consideration of both of these key effects required by the General theory of relativity, which predicts how objects affect the geometry of space-time around them.
Second, at the disposal of scientists there was not enough computing power to account for the magnetic turbulence or perturbations within the accretion disk. These perturbations allow the disk particles to stick together and keep a round shape, eventually letting the gas disk to sink into a black hole.
“Imagine that you have this thin disk. You face the task is to separate the turbulent flow inside the disk. This is a really difficult task,” says Checkowski.
Without possibility of separation of these parts of astrophysics are unable to realistically simulate realistic black holes.
Modeling black holes
To develop a computer code capable of modeling the inclined accretion disks around black holes, Liska and Cekovski used instead of Central processor units (CPU) graphics (GPU). Extremely effective in creating computer graphics and image processing, graphics processors accelerate the creation of images on the screen. Compared to the CPU, they are much more efficient in computing algorithms that process huge amounts of data.
Chekovski compares GPU with 1000 horses, and the CPU with Ferrari with an engine power of 1000 horsepower.
“Imagine that you are moving into a new apartment. Many times you have to travel from your apartment to the Ferrari, because it is placed not very much Luggage. But if you could put one box on each of the thousands of horses that could be transported all the things at once. This is the power of the GPU. It has many components, each of which individually is slower than the CPU, but a lot of them,” explains Chekovski.
Moreover, adds Liska, for their measurements they used a method of adaptive grinding of the computational grid that uses a dynamic grid, changing and adapting to the flow of traffic throughout the simulation. This method allows to save energy and computing resources, focusing only on certain blocks where, in fact, occur flow.
The researchers note that the use of GPU has speeded up the modeling, and the use of adaptive mesh to increase the resolution of this simulation. Eventually, scientists were able to create a model of a very thin accretion disks with a ratio of height to radius of 0.03. Modeling such a thin drive, the researchers were able to see the equation of the plane of the accretion disk near a black hole.
“The most subtle of the simulated disks had a height to a radius of about 0.05, and found that interesting things happen only when index of 0.03,” says Checkowski.
Astronomers say that even with such thin disks, black holes still emit strong jets of particles and radiation.
“Nobody expected to see such thin disks are able to throw away the jets. Everyone expected that the magnetic fields that create these jets, tear these thin discs, and yet they are still there, and because of this, we can solve such Supervisory puzzle”, says Checkowski.
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