When black holes appear as stars collapse, they momentarily eject jets of material that literally slow their rotation until it stops completely. Most black holes can spin much more slowly than expected. When a star collapses to form a black hole, it releases a powerful jet of energy that slows the black hole’s rotation to nearly zero within minutes. The rotation of a newborn black hole is determined by two opposing processes. When fast-moving matter enters its orbit, the black hole gains energy and accelerates its rotation. But it is precisely this absorption that causes the black hole to eject a huge jet within minutes, causing a loss of energy and slowing its rotation. Astrophysicist Jonathan Jacquemin-Ide of Northwestern University in Illinois and his colleagues used a series of simulations to understand how the two processes interact and what happens after black hole formation is complete. I understood what was happening. They discovered that collapsing stars (the name given to black holes, which are formed by the collapse of stars and make up most of our universe) should not rotate at all. “So far, in most studies, scientists have not taken into account the reduction in the black hole’s rotational speed when material is ejected. So in the simulation, all the black hole did was eat, eat, eat gas. And she changed it more and more. Therefore, we expected the black hole’s spin to reach its maximum value,” says Jackman-Ide.
Astronomers measure a black hole’s spin using a dimensionless parameter called spin or α. If α 0, the black hole does not rotate at all. If α 1, it will rotate at the fastest possible speed for an object of that mass. The researchers found that shortly after birth, the collapsers rotate with a dimensionless rotation of about 0.2 or slightly less. “This shows how powerful the jet stream is,” says Jackman-Ide. “What surprised me most is that this is happening so quickly. There are events that last perhaps 100 seconds, during which time the way the black hole rotates can completely change.” This is consistent with what astronomers have observed from gravitational waves, ripples in space and time caused by the motion of large cosmic objects. This is consistent with what astronomers have observed from gravitational waves, ripples in space and time caused by the motion of large cosmic objects. The Laser Interferometer Gravitational-Wave Observatory (LIGO) has detected waves from about 100 black hole mergers. And all measurements confirm that the dimensionless spin of black holes before merging is typically within 0.2. “With gravitational waves, we can study the evolution of a black hole at a very specific point in its life, the moment at the end of its life, and before that it was doing something completely different for billions of years. “We can do that,” says Katerina Chatzioannou. California Institute of Technology. “With this work, we were able to add another piece to the puzzle of her life.” This new discovery could also help distinguish between different types of black holes. “Besides the collapse of a star, there are other ways black holes can form. They are probably less common, but they do exist,” Chatzioannou says. “Until recently, I didn’t know how to tell them apart, but now I know better how to tell them apart.” Black holes that have undergone a merger typically have a higher spin than the “baby” collapsers that researchers study, close to 0.7, so measuring the spin rate of a black hole is a difficult task for scientists to helps us understand the past. The spin of a black hole (BH) forming at the center of a massive star changes from its initial value under the influence of two competing processes: the angular momentum of accreting gas, which increases the spin, and the angular momentum of ejection. Masu. From BH, the spin decreases. Ultimately, the final equilibrium spin is established by the balance of both processes. The magnetic field of a black hole plays an important role in the formation of relativistic jets and gamma-ray emission (GRB). The magnetic field of a black hole plays an important role in the formation of relativistic jets and gamma-ray emission (GRB). In this study, the scientists investigated a model of the magnetic accretion disk (MAD) that drives the spin evolution of the BH. By applying Lowell’s MAD BH spin evolution model to collapsing stars, the authors show that when a black hole accumulates to about 20 percent of its original mass, its dimensionless spin necessarily increases to a small value of α≠0.2. was shown to reach. Regarding the mass accretion rate from such spin and collapsing star simulations, experts believe that the new analytical model can reduce the energy of a typical GRB jet, Ljet ≤ 1050 (10^50) erg s-1 (s^-1) demonstrated that it can be reproduced. Furthermore, the scientists showed that the model they developed reproduced the nearly constant performance of a typical GRB jet. A delayed onset of the MAD process results in a stronger jet at the top of the GRB glow (Ljet ≡ 1052 (10^52) erg s-1). However, the final spin remains low (α² 0.3). These results are consistent with the low spin obtained from gravitational wave observations of binary black hole mergers.
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