Black holes are characterized by two simple properties: mass and spin. While astronomers have long been able to measure the mass of black holes fairly effectively, determining their spin rate has been a much more difficult task.
Astronomers using NASA's X-ray Chandra Telescope and the European Space Agency's Newton Parallel Telescope, as well as the Hubble Space Telescope, which observes visible light and frequencies close to it, have discovered a rapidly spinning massive black hole 6 billion light-years away. The first measurements of the spin rate in such a distant black hole is an important advance in understanding how black holes grow over time.
Black holes are characterized by two simple properties: mass and spin. While astronomers have long been able to measure the mass of black holes fairly effectively, determining their spin rate has been a much more difficult task.
In the past decade, astronomers have proposed ways to estimate the spin rate of black holes at distances greater than a few billion light years. This means that we are viewing the regions surrounding black holes as they looked billions of years ago. However, determining the spin rate of these distant black holes required several interdependent steps.
"We wanted to skip the mediation, and calculate the spin of black holes throughout the universe," says Rubens Rice of the University of Michigan in Ann Arbor, lead researcher in a paper published in the March 5, 2014, online issue of the journal Nature.
Rice and his colleagues calculated the spin of the supermassive black hole pulling in the gas around it, producing an extremely luminous quasar known as RX J1131-1231. Due to the luck of the researchers who took advantage of an alignment with a large galaxy passing through, the space-time disturbance caused by a huge elliptical galaxy that stood in the line of sight, and acted as a gravitational lens that magnified the light from the quasar. Gravitational lensing, whose existence was first predicted by Einstein, offers a rare opportunity to study the innermost regions of quasars by acting as a natural telescope and amplifying the light from these sources.
"Thanks to the gravitational lens, we were able to obtain detailed information on the X-ray spectrum, that is, the amount of X-rays visible at different energies from RX J1131-1231," said one of the co-researchers in the study, Mark Reynolds, also from Michigan. "These data in turn allowed us to get an accurate value for the speed at which the black hole rotates."
The X-rays are produced in the absorption disk of the gas and dust surrounding the black hole and create a cloud in which a temperature of millions of degrees exists, this is the corona next to the black hole. The X-rays from this ornament reflect the interior of the accretion disk. The strong gravitational forces near the black hole change the spectrum of the X-rays. The larger the change, the more the rays came from an inner region of the absorption disk and were closest to the black hole.
"We estimate that the X-rays come from an area in the disk located only 3 radii from the event horizon, the point of no return for the material falling into the black hole," says John Miller from Michigan, another researcher who is involved in the study.
"The black hole must be spinning very fast to allow the disk to survive at such a small radius."
By measuring the spin of a distant black hole, the researchers discovered important clues about the growth process of black holes. If black holes grew mainly through collisions and mergers between galaxies, they should accumulate material in a stable disk, and receiving a steady supply of new material would lead to a rapid spin-up of the black holes. Conversely, if the black hole grows through many small accretion events, they will absorb the material from different directions and this may slow down the rate of rotation.
The discovery that the black hole in RX J1131-1231 is spinning at more than half the speed of light is indeed consistent with the age of this black hole, 7.7 billion years after the Big Bang, and that it grew through mergers and not through pulling materials from different directions.
The ability to measure the spin of the black hole over large cosmic ranges can allow direct research as to whether black holes evolve at the same rate as their host galaxy? The spin measurements of the black hole RX J1131-1231 are a major step along the path of demonstrating techniques for using X-ray telescopes to study distant supermassive black holes. Prior to this study, most distant black holes whose direct spins were calculated were located at distances of 2.5–4.7 billion light years.
For information on the NASA website
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Chaim P
A massless photon has linear momentum. Isn't that strange to you? Why do you go for the complicated stuff, when the simple ones don't make sense?
Thanks to Zvi for the effort
And now, of course, more questions arise.
Why would the event horizon be limited to the speed of light? It is not a body, but a domain. Every rotating body has an imaginary shell at a great distance that rotates with it at a speed greater than the speed of light. It is impossible to transfer information through it, and it does not contradict the theory of relativity.
And what is the meaning of angular momentum if the mass has a radius of 0, unless you completely give up on Newton's equations. (in the equation of angular momentum the radius appears in the denominator)
more and more. This is probably not the right place.
deer
Thanks for the explanation.
Miracles and life.
I agree with you that the definition here is very problematic - when you say the size of a black hole you have to specify.
A Schwarzschild black hole (non-rotating black hole) has only one "size" - the Schwarzschild radius (the horizon) which an object with a smaller radius can never escape from the black hole, no matter what it does. According to the standard theory such a black hole is completely empty and all its mass is in the center. However, mass is not the only property that defines a black hole - according to the "no hair" theorem, there are three quantities that characterize a black hole - the mass, the charge and the angular momentum (of course, angular momentum is a vector and is therefore a magnitude and a direction).
When a black hole has angular momentum (such a black hole is called a kerr black hole) its structure is not simple. Although the horizon is still spherical but double, there is an inner horizon and an outer horizon - later I will expand a little on one of the results of this.
Also, the outer horizon of the black hole is surrounded by an ellipsoid shell (a flattened sphere) called the "argosphere". A particle that is in the argosphere can leave, but inside the argosphere it cannot stand and must turn (mathematically, the coordinate relating to rotation mixes with the time coordinate - therefore, just as in normal space you must move forward in time, here you must rotate in the same direction as the black hole).
Finally, the singularity is not a point as in the case of a Schwarzschild black hole, but a ring - this is the result of the existence of two horizons and this means that a body that falls into the black hole does not have to reach the singularity (unlike the Schwarzschild case), it can reach the center of the system and pass through the surface blocked by The ring The surface blocked by the ring is an interesting thing - in fact, it infects two different spaces, that is, it constitutes a wormhole, but it seems that in practice it is not possible to pass through it (since passing through it would damage its stability).
So now we can talk about what was said here.
As I started, I think the definition here is quite bad, in practice I think this is about the speed of the outer horizon. This speed cannot be higher than the speed of light as this would cause the ring that constitutes the singularity to go outside the horizon - this is known as a naked singularity and there are good reasons to think that it is not possible.
In any case, the fact that the rotation speed is half the speed of light is not surprising - the typical scale here is the speed of light. Moreover, there were already previous estimates of the spin of black holes and these indicated a rotation at a high speed close to the maximum possible.
Chaim P
The radius of the black hole is certainly not 0. The black hole is defined by position and radius. The radius is the same distance from the center of the hole that the escape velocity is the speed of light.
What's more - the material probably shrinks to a radius of 0.
Its angular momentum is a vector, meaning it is defined by magnitude and direction. Therefore - 2 data are enough to define the black hole - mass and angular momentum.
The earth is flat because its volume has mass. Black hole all mass is concentrated in its center at a point. The black hole is, as far as I understand, a perfect sphere.
Who understands, who knows?
"The black hole in RX J1131-1231 is spinning at more than half the speed of light"
(It's interesting that I identified the problem like my predecessors, Avi Luz, and performed a cut-and-paste just like him 🙂 )
The sentence is puzzling. Speed Black should rotate X times per second. It has nothing to do with the speed of light!
Another question
From what I've read, the radius of the black hole is zero. So how are you supposed to measure "X times per second?" Newton argued for the conservation of angular momentum. If a mass collapses into a black hole, it must conserve the angular momentum it had. But what does angular momentum mean for a body whose radius is zero? I conclude from this that the radius of the black hole is a really positive magnitude. Always positive and under all conditions. is that so? Has anyone given their opinion on this matter?
Another question - follow-up question to the above:
Quote from the article: "Black holes are characterized by two simple properties: mass and spin"
I think that is inaccurate. Three characteristics: mass, spin, and direction of spin. The angular momentum has a direction and the direction is also conserved. Here, too, I come to the conclusion that the radius of the black hole is a positive magnitude at the equator, and a zero magnitude in the direction of the poles. (The Earth is also flat because of this principle). Has anyone given their opinion to these things.
Thank you for a professional answer. I am, of course, not a professional physicist.
Life
"The black hole in RX J1131-1231 is spinning at more than half the speed of light."
In my understanding, "spin" is angular momentum. and therefore its units are different from units of "speed"
Avi Luz
Stunning