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.
Questions tagged [accretion-disk]
91 questions
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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 of gravitation?
0x90
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Putting the importance of the blackhole image into perspective
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 imaging technique and data analysis algorithms,…
user929304
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Why don’t black rings exist in 3+1 dimensions?
In higher dimensions black holes can take different forms. Besides spheroids, there are also “black rings” which have a toroidal event horizon. However, in our 3+1 dimension no black ring solution has been found. The only valid solution of a black…
哲煜黄
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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 currently working to implement Kerr black holes as…
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Need advice on thin accretion disk model
I'm a physics teacher and I'm building a simple accretion disk model to show to students in an astrophysics class (undergraduate level), as an exemple of physics modeling. I need to know if this model is credible enough, and what references there…
Cham
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How long does it take a black hole to eat a star?
I presume the answer is that it depends on the mass and size of the star and black hole and how they approach either other, but I was wondering if somebody could provide some rough bounds (e.g. hours vs thousands of years) theorized or based on…
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Why is the common envelope ejected in some accretor-donor systems?
As an example, let us consider a binary system of a neutron star and an evolved star (e.g. red giant) that has expanded, filled its roche lobe, and started the mass transfer onto the neutron star.
Under certain conditions such mass transfer can…
Gianluca
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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?
Nayeem1
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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)
$$\mathcal{U}_{eff}=-\frac{1}{2}\ln\left|g^{tt}-2lg^{t\phi}+l^2g^{\phi\phi}\right|$$ where…
Richard
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Is the average temperature of a big accretion disk colder than a small one?
Suppose we have a Shakura and Sunyaev style accretion disk between $r_1$ and $r_2$. What is the average temperature? We can calculate it by integrating the local temperature $$T(r)=\left [ \frac{3GM\dot{m}}{8\pi\sigma r^3}\right ]^{1/4} \left…
Anders Sandberg
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The difference between sub-Eddington and super-Eddington accretion disk models
I am studying accretion disks around active galactic nuclei (AGN). I have seen two sets of models, sub-Eddington and super-Eddington accretion disks. What do these terms refer to in this case? I understand that the Eddington luminosity has something…
Sean Mooney
- 75
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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 thinking maybe it gets eject or sucked in completely.…
Pugs
- 97
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Why can't friction in an accretion disk radiate away enough of the angular momentum do create inward spiral?
As almost every source that I'd found explains, it was a challenge for scientists to understand the mechanism by which the total angular momentum in the accretion disc was conserved, while taking the latter (total conservation of angular momentum)…
Max
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Why does a black hole grow when it consumes matter? Isn't this a contradiction?
I've been thinking about this for a while but can't get my head around it.
A black hole's mass is such that its gravity can overcome light. Its event horizon, as I see it, is the boundary up to which light is "pulled back" into the black hole, from…
ScaryAardvark
- 173
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Angular momentum in an accretion disk
I need to plot the time evolution of the total angular momentum in an accretion disc. This confuses me because I thought this should be constant, since angular momentum has to be conserved?
I'm given the angular velocity…
Alex M
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