Although structures like jets emit in the X-ray region of the spectrum, the X-ray band is dominated by the disc and corona. And so X-ray jet emission can be hard to detect in the region directly surrounding the black hole. Jet emission is more commonly associated with radio wavelengths.
비록 제트분출과 같은 블랙홀 주변의 구성물들이 전자기 스펙트럼 중 X 선 영역에서 복사를 일으키긴 하지만 X 선 대역에서 방출이 지배적인 곳은 (강착)원반과 코로나 이다. 따라서 X 선 분출은 블랙홀의 주변에서 직접 방출이 검출되지 않는다. 전파 파장대역의 전자기파를 주로 방출하는 곳은 주로 제트 분출이다.
In this lesson, we will take a look at the spectrum of a black hole and see why this may be the case. And explore the mechanism that creates this emission, discovering what this can tell us about black hole systems.
이번 강의는 블랙홀[주변 구조물에서 방출되는 빛]의 스펙트럼을 살펴본다. 그리고 그 스펙트럼의 근인이 무엇인지 알아본다. 그 빛을 뿜어내는 구조물의 기작을 살펴보고 블랙홀 시스템[블랙홀과 그를 둘러싼 여러 구조물 사이의 상호작용]을 알려줄 수 있는지 살펴보기로 하자.
이번 강의는 블랙홀[주변 구조물에서 방출되는 빛]의 스펙트럼을 살펴본다. 그리고 그 스펙트럼의 근인이 무엇인지 알아본다. 그 빛을 뿜어내는 구조물의 기작을 살펴보고 블랙홀 시스템[블랙홀과 그를 둘러싼 여러 구조물 사이의 상호작용]을 알려줄 수 있는지 살펴보기로 하자.
If we return to the plot we have been examining during this module, we can see the addition of this new radio component. From right to left, this new component begins in the same region of the plot as the spectrum of the disc and the corona. The overlap in this region of the spectrum is due to all three components emitting a portion of their energy in the X-ray band. The new radio component then extends to longer wavelengths, or lower photon frequencies, peaking and then tailing off into radio frequencies.
The jet of the black hole is responsible for this new component of the spectrum. Jets are powered by synchrotron radiation, energizing photons through interactions with electrons, that are trapped in circular orbits around the magnetic field within the jet.
While we don't fully understand the mechanism that is used to launch the jet, astronomers suggest that the magnetic fields within the jet can be thought of as a tangled mess of spaghetti, that has been stretched out in one direction. This stretched out spaghetti causes the jet to transfer energy and angular momentum into the surrounding area. Particles energized within the jet can extend out to incredibly large distances.
Similar to the multicolored disc model, accurate descriptions of jets require us to consider smaller slices, in order to account for the different energies supplied by the synchrotron emission.
If the jet is cut up into narrow disks along its length, like slicing up a banana into small circular pieces. We can plot the spectrum of synchrotron emission from each of these disks. As we move away from the central black hole, the number of particles decreases, along with the strength of the magnetic field. By adding the contribution from each disc of the jet, we can recreate the spectrum of the jet.
One mystery astronomers are trying to solve, is why there appears to be two types of jets around black holes. The first type of jet is a continuous jet and just like water spouting from the nozzle of a hose, the continuous jet is a continuous stream of particles, constantly flowing outward along the path of the jet.
The second type of jet has multiple names, but it is seen as clumps of particles being emitted out of the jet. Scientists call these clumps, burps, bullets, or ejecta. Just like the continuous jet, jet ejecta provide a route for the spread of energy and angular momentum into the area surrounding a black hole. As a result, jets can sometimes be a mechanism to feed back energy into the region surrounding the black hole system.
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In this module, we have not yet considered how the orientation of the black hole system affects our observations. Since the jets tend to align with the spin axis of the black holes, the direction of their spin determines which way the jets point and how much light escapes.
If we are viewing a black hole system with the accretion disc from the side, the jets appeared to extend perpendicular to the center of the disc. If, on the other hand, we see the accretion disc from the top down perspective, the jet is pointed directly at us and appears to be much brighter. This is because the emission is beamed towards us, increasing the energy of the photons we receive.
If the system is at an intermediate angle, we will see a blue shift in the jet pointed towards us, while the jet angled away from us will be red shifted. We will also see that the jet angled in our direction is brighter than its counterpart. We should note that this difference in brightness and color is due to the beaming effect. It does not mean that one jet is actually more powerful than the other, or that they're emitting different wavelengths.
If the jet is offset from the spin axis of the black hole, then we may be able to detect a wobble from the jet. This has been recently seen in observations of the black hole binary known as V404 Cyg. A research team, including professors here at the University of Alberta, have been looking at V404 Cyg, to investigate its jet in more detail.
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[인터뷰] [커세라 페이지]
What types of jets could a black hole have?
Interview with Dr. Gregory Sivakoff, Professor at the University of Alberta
So the material comes into the black hole, falls onto the black hole. If you have your accretion disk, roughly speaking, there is a jet perpendicular to the accretion disk.
During the initial stages of the outburst, there is a jet which is like one continuous long burp. It's just a jet coming out. Sort of maybe imagine your water hose, you turn your water hose on and your water is coming out, except this is probably more like a cone of material coming out. It's a very, very narrow cone of material coming out in both directions, perpendicular to disc.
So that's what we call a compact steady jet. We call it a compact jet because it turns out that with all of our best instruments, we can't really see the structure of this too well as we go down the jet. We can tell some of it but we can't tell in detail.
Now it turns out that black holes have another type of jet behavior. And they undergo a switch where all of a sudden they go from this, sort of nice little compact steady jet to a sudden burst where instead of the compact steady jet, that compact steady jet seems to be gone. And you get these blobs of material that go out with time.
So these blobs of material are jet ejecta. In the Canadian press, we call these things black hole burps. The Americans call them black hole bullets. One of the reasons why they're called bullets, perhaps, in the American press, is that we talk about the trajectory that these things have. And so these objects go in a straight line. And that trajectory is called a ballistic trajectory. And so, it is not a small stretch to go from a ballistic trajectory to a black hole bullet.
The particular press release officer at the University of Alberta was not a fan of that particular description and went with burps. I think it's a wonderful analogy because we can talk about the feasting that the black hole is doing and relating it to their burps. Although they have different types of burps. Some are sort of your short staccato burps, and some of them are these long continuous burps.
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