Questions tagged [accretion-disk]

An accretion disk is the disk around a compact star that accumulates matter from e.g. a companion star by the Roche lobe overflow or stellar wind transfer.

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What does a black hole accretion disk look like edge on?

We have images of two black holes so far, with representations showing a deep black center where in-falling matter vanishes- how would that look side on? Would it be possible to even obtain an image ...
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What determines the black hole accretion rate?

There is clearly a natural timescale to accrete matter around a black hole given by the balance of pressure and gravity, known as the Eddington luminosity. However, as I understand it, this is really ...
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Rotating black hole

I know that everything that is shaped from gravity force is rotating, and gravity is a central force. but I want to know how can we detect that a black hole has an angular momentum? By which ...
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Neutrinos and black holes

As a new user I could not comment on Do neutrinos of any flavor get trapped in black holes? My question is that the Ice Cube facility has mapped Neutrinos coming from black holes, as stated in ...
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Improving physics simulation of black hole accretion disk?

I have recently been working on software which uses ray tracing/marching to render a black hole in the Schwarzchild metric. I've implemented most everything that I originally set out to do, and I am ...
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What are the applications of the relativistic von Zeipel's theorem in the theory of accretion disks around rotating black holes?

I am reading the paper, The Relativistic von Zeipel's Theorem, where the relativistic version of the classical von Zeipel's theorem is discussed. According to von Zeipel's paper, A rotating system of ...
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If the BH accretion disk rotates near the speed of light should its EM-radiation in direction of rotation be highly blueshifted?

If the BH accretion disk rotates near the speed of light should its EM-radiation in direction of rotation be highly blueshifted? Maybe gamma blushifted if there weren't gravitational redshift?
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Stress Tensor for a cylindrical Accretion Disk

For a thin accretion disk how do I prove that the stress tensor has only Trφ and Tφr components equal to $μr dΩ/dr$ ? My trouble is the derivation of the divergence in cylindrical coordinates for the ...
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Circular gravitational field

Why do all heavy masses in the universe always have circular gravitational field and why do objects 'falling' under their spacetime influence always fall in circles? For example, accretion disks ...
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Show how to obtain the mass accretion rate $Ṁ = -2πRvRΣ$ from Navier-Stokes mass conservation $∂ρ/∂t + ∇ · (ρv) = 0$ using cylindrical coordinates

Consider a steady, cylindrical, slim axisymmetric magnetized disk of average density $ρ$, surface density $Σ$ and semi-thickness $H$, around a Neutron star. Within a slim disk, rotational velocity $vR$...
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Would a black hole act as a particle accelerator between the photon sphere and the event horizon?

I'm trying to understand the behavior of photons between the photon sphere and the event horizon. Here is what I think I understand so far : the radius of the PS is 1.5 times the Schwarzschild radius ...
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Is accretion disc caused by frame dragging?

Is accretion disc around a Kerr black hole the result of its frame dragging?
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What happens when a cool brown dwarf slowly accretes matter?

Let's imagine that we take a brown dwarf close to the minimum mass of a red dwarf. Then let's allow it a few quadrillion years to cool. Finally slowly accrete matter at a rate of say 1 Jupiter mass ...
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What happens when a helium white dwarf accretes enough matter?

What happens when a helium white dwarf accretes enough matter? Say you have a white dwarf made of helium, what happens when it's core becomes dense enough to fuse helium and how massive would it have ...
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Is a fusion process possible inside an accretion disk?

Is a fusion process possible inside an accretion disk? As the speed of matter inside an accretion disk approaches the speed of light can an incoming object collide with the disk material and cause a ...
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Why doesn't earth have a hydrogen atmosphere if hydrogen's thermal velocity is 1.75 km/s - less than 1/6th of earth's escape velocity? [duplicate]

I have read that in order to retain a gas, a planet's escape velocity must be at least six times the thermal velocity of that gas (I understand that this is just an approximation of the Maxwell ...
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How can supersonic accretion flows exist in astrophysical scenarios?

I often hear about supersonic accretion flows in astrophysical scenarios: for example, the inner parts of the accretion disk around a supermassive black hole or cold filaments accreting into galaxies ...
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Does some of accretion disk light make focal points above the black hole poles? [duplicate]

Does some of accretion disk light make focal points above the black hole poles?
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Does the latest picture of EHT mean the end to the no hair theorem?

I couldn't help but noticing what looks like "hair" in the latest image from EHT. Does this mean the end of the no hair theorem? Pun intended but also a serious question.
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What ranges of $l$ and $m$ give the spherical harmonics for disk features?

The spherical harmonics represent a spherically symmetric basis and correspond to the eigenfunction solutions of the three-dimensional Laplacian. They take the form $$ Y_l^m(\theta,\phi) = \sqrt{\frac{...
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Are the particles in the accretion disk in free fall around the black hole?

I know that black hole can feed off the material in the accretion disk and gain mass, the accretion disk is also powered by the black hole to move at a fraction of speed of light. I am wondering are ...
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Are there black holes without accretion disk but emitting astrophysical jets?

First a citation from Wikipedia page about relativistic jets: "Jets may also be observed from spinning neutron stars. An example is pulsar IGR J11014-6103, which has the largest jet so far ...
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Why does the jet come out perpendicular to the accretion disc?

Why does the jet always come out perpendicular to the plane of the accretion disc around a black hole?
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Is the Accretion Disk of a Black Hole just an illusion?

As a matter of fact, I recently learnt that as an object is approaching a black hole, to an outside observer the object seems to be getting slower and slower and will cross the event horizon after an ...
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I have a couple of questions regarding the physics of planet Miller and the black hole it's orbiting from the movie "Interstellar" [closed]

I watched the movie and thoroughly enjoyed it. I had a couple of questions regarding the physics, so I looked for answers. I got them, but I was left even more questions. I know that a lot of these ...
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Some doubts regarding the Paczynsky-Wiita potential for modeling accretion disk around Schwarzschild black holes?

I am presently studying accretion processes around Schwarzschild black holes and for this purpose I am reading the classic paper by Paczynsky and Wiita (1980). In this paper, the authors define the ...
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Is an exact description of accretion flow possible very close to a Schwarzschild black hole?

While modelling accretion disks around Schwarzschild black holes, various pseudo-Newtonian potentials are prescribed and then compared to general relativistic results. Though the pseudo-Newtonian ...
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Physical importance of centrifugal force and Coriolis force in the context of the restricted 3-body problem

In the textbook Galactic Dynamics (Binney and Tremaine), the restricted three-body problem to find the trajectory of a test mass that orbits in the combined gravitational field of two masses $M$ and $...
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What happens to the accretion disk when two black holes merge?

I'm aware that accretion disks around black holes are formed from the swirling mass of matter that is slowly being stripped of its atoms, but what happens to it when two black holes merge? I was ...
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AGN accretion disk double peak explained?

I have a question to the following lecture: https://ned.ipac.caltech.edu/level5/Fabian4/Fab2_2.html In Figure 3 it says that a narrow annuli of a Newtonian disk should alrdy show a double peak ...
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Effective potential for Kerr geometry

In the review Foundations of Black Hole Accretion Disk Theory, the authors defines an effective potential for Kerr geometry as (Chap. 2, eqn. 23) $$\mathcal{U}_{eff}=-\frac{1}{2}\ln\left|g^{tt}-2lg^{t\...
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Newtonian/Relativistic Solutions of Fluid Disks in orbit around a massive body

I have been trying to make an RMHD (Relativistic Magneto-Hydro Dynamics) Set-up of a Disk around a Massive Rotational Body. The initial paper I have been studing a paper which uses a Fishbone & ...
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Physical significance of angular velocity of orbits around Kerr black holes

For the Kerr metric $$ds^2=\left(g_{tt}-\frac{g_{t\phi}^2}{g_{\phi\phi}}\right)dt^2+g_{\phi\phi}\left(d\phi-\omega dt\right)^2+g_{rr}dr^2+g_{\theta\theta}d\theta^2$$ the angular momentum is defined as ...
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What are Quasi-Periodic Oscilations and how can they be used to determine the mass of black holes?

Quasi-Periodic Oscillations (QPOs) are observed in almost all accreting systems and they provide an essential tool to explore accretion flows from compact objects. But I couldn't understand what ...
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Four-momentum of a photon emitted from an accretion disk

Consider a non-rotating compact object surrounded by a revolving accretion disk. A distant observer sees the disk in an edge-on position. The center of the disk may be taken as the origin of $r-\theta-...
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How can a gas be in circular orbit when centrifugal force is dominant in an accretion disk around a black hole?

In the textbook "Black Holes, White Dwarfs and Neutron Stars: The Physics of Compact Objects" by Shapiro and Teukolsky, the author makes the following statement while discussing the standard thin disk ...
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Disk-like structures spectra vs ring spectra?

In the introduction to this paper (https://arxiv.org/abs/1803.06423) it is mentioned that disk-like spectra was observed in black hole X-ray binaries, when models would expected to be unstable (...
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What causes the heating of a black hole's accretion disk?

Sheperd Doeleman said in a TED video that the accretion disk is heated by friction. Is that correct? I thought it might be adiabatic heating from the compression of the gasses.
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Can Compton scattering increase a photon's energy?

I've read (in Hagai Netzer's book The Physics and Evolution of Active Galactic Nuclei) that "Comptonization in the [black hole's accretion] disk atmosphere can increase the energy of some photons..." [...
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Understanding the notion of lose or win of angular momentum in accretion disk

Here is below a slide of one of my lecture in planetology : I understand well the fact that ring A will be slow down by friction with ring B since ring B is rotating slower and the inverse process (...
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Wind-fed Accretion and White Dwarf stars

Can a White Dwarf star in a binary system accrete matter via the Wind-fed accretion process?
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Does infalling material leaves a detectable imprint on the black hole's event horizon?

An external observer will never see anything cross the event horizon, and in most explanations the story ends here. But I wonder what happens with gravitational effects of the material? For example ...
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Putting the importance of the blackhole image into perspective [closed]

The recent astonishing achievement of obtaining an actual image of a blackhole, resulted from a massive collaborative work using 8 different telescopes and the equally on par efforts in developing the ...
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Why isn't the circumferential light around the M87 black hole's event horizon symmetric?

After the revelation of the first black hole images, it seems there is a bias towards the south side. Is it because of measuring it from earth or is it something more fundamental in the understanding ...
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How can write physics in terms of local rest frame?

Many times I saw that people wrote that we write the equations in terms of local rest frame, for example in the paper of Novikov and Thorne that calculated stress-energy tensor for Kerr blackhole ...
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How to calculate the corotation radius?

I am studying this paper: P.Ghosh & F.K.Lamb, APJ, 232, pag.259 (1979) I do not understand how the authors calculate the corotation radius, $r_{co}$, where the matter of the disk has the same ...
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If you fell into a black whole with an accretion disc, but perpendicular

If you fell into a black whole with an accretion disc, but orthogonal to the plane of the disc - would you ever meet the disc? I'm not asking whether you survive long enough, and obviously we assume ...
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How can a galaxy not be disk shaped [closed]

If a galaxy is the accretion disk for a supermassive black hole, how can it be a shape other than disk?
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Neutron Star LMXB Accretion Spin-Up Estimation

I've been asked to estimate how much mass a neutron star in a low mass X-ray binary would have to accrete in order to be spun up to ~300 Hz. I found the conservation formula $\frac{d(I\omega)}{dt} = \...
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Why does the accretion disc radiate energy and matter?

Jets of matter and energy are powered by accretion disc i.e., matter spiralling into the massive black hole at the galactic centre. How is this jet formed? I think that the dust particles and gases ...
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