<p>Let me give an answer based on my intuitive understanding of the thing...</p>

<h3> Initial conditions</h3>

<p>The initial accretion disk movement is defined by the objects falling into it, the black hole's mass and its spin of course.</p>

<p>If you take the situation where a single star falls on a quiet black-hole, the accretion will appear along the orbit of the infalling object.</p>

<p><a href="https://i.sstatic.net/opCmx.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/opCmx.png" alt="enter image description here"></a>
<sup>Credit: NASA, S. Gezari (The Johns Hopkins University, Baltimore, Md.), A. Rest (Space Telescope Science Institute, Baltimore, Md.), and R. Chornock (Harvard-Smithsonian Center for Astrophysics, Cambridge, Ma.)</sup> and live on <a href="https://www.youtube.com/watch?v=CpaVzOKihBQ" rel="nofollow noreferrer">youtube</a>...</p>

<h3> Equilibrium in an active galactic nucleus</h3>

<p>Now on the long run, if additional matter is constantly coming in, at first thought I would think </p>

<ul>
<li><p>the accretion disk momentum will be exchanged with the one of the black hole through the <a href="https://en.wikipedia.org/wiki/Penrose_process" rel="nofollow noreferrer">Penrose process</a>, </p></li>
<li><p>Infalling matter momentum will reflect the overall host galaxy momentum - especially if the galaxy is a spiral </p></li>
</ul>

CC BY-SA 4.0
2018-08-10T06:11:06.800Z
fyi I have just asked [Has the Penrose process ever been linked to an observed phenomenon in some way?](https://astronomy.stackexchange.com/q/27298/7982)
uhoh
CC BY-SA 4.0
2018-07-19T06:55:52.623Z
2019-04-11T22:23:44.203Z
2019-04-11T22:23:44.203Z
J. Chomel
<p>The question <a href="https://astronomy.stackexchange.com/q/26987/7982">Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A*?</a> about just how close to edge-on we would be viewing any accretion disk around the black hole in the center of our galaxy, and @Zephyr's <a href="https://astronomy.stackexchange.com/a/26988/7982">excellent answer</a> have got be thinking about the geometry and angular momentum.</p>

<p>While the angular momentum vector of a black hole will likely reflect that of all the matter that fell into it , would the plane of any accretion disk around a black hole reflect the black hole's <em>current equatorial plane</em>, or a plane defined by rotation of whatever material is currently falling in to it?</p>

<p>Another way to formulate this question might be to propose an incredibly unlikely <a href="https://en.wikipedia.org/wiki/Thought_experiment" rel="nofollow noreferrer">Gedankenexperiment</a>. If I inserted a black hole into the center of a rotating disk of material so that the black hole's axis <em>was in the plane of the disk of material</em> rather than parallel to its rotational axis, would a well-defined accretion disk form all all, and if so, what would determine the orientation of that plane?</p>

CC BY-SA 4.0
2018-07-19T02:39:51.847Z
I think your question would be better served if it was phrased differently. As it is, it seems like you're asking if *any* black hole can have the configuration you describe (which it could). Perhaps the better question is to ask about a specific black hole or ask about what the population of black holes are like overall.
zephyr
CC BY-SA 4.0
2018-07-19T03:27:35.917Z
@zephyr I'm trying to find out which tends to defines the orientation of the plane of a black hole's accretion disk, the plane of rotation of the in-falling matter, or the plane of the black hole's equator, or both, or if they are significantly misaligned, would that just not lead to a well-formed disk to begin with.
uhoh
<black-hole><supermassive-black-hole><accretion-discs>
What defines the plane of an accretion disk around a black hole?
uhoh
# What defines the plane of an accretion disk around a black hole?

(Asked by: username_0 on 2018-07-19)

The question [Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A\*?](https://astronomy.stackexchange.com/q/26987/7982) about just how close to edge-on we would be viewing any accretion disk around the black hole in the center of our galaxy, and @Zephyr's [excellent answer](https://astronomy.stackexchange.com/a/26988/7982) have got be thinking about the geometry and angular momentum.

While the angular momentum vector of a black hole will likely reflect that of all the matter that fell into it , would the plane of any accretion disk around a black hole reflect the black hole's *current equatorial plane*, or a plane defined by rotation of whatever material is currently falling in to it?

Another way to formulate this question might be to propose an incredibly unlikely [Gedankenexperiment](https://en.wikipedia.org/wiki/Thought_experiment). If I inserted a black hole into the center of a rotating disk of material so that the black hole's axis *was in the plane of the disk of material* rather than parallel to its rotational axis, would a well-defined accretion disk form all all, and if so, what would determine the orientation of that plane?

**Tags:** black-hole, supermassive-black-hole, accretion-discs
> **Comments:**
> **username_1**: I think your question would be better served if it was phrased differently. As it is, it seems like you're asking if *any* black hole can have the configuration you describe (which it could). Perhaps the better question is to ask about a specific black hole or ask about what the population of black holes are like overall.  
> **username_0**: @zephyr I'm trying to find out which tends to defines the orientation of the plane of a black hole's accretion disk, the plane of rotation of the in-falling matter, or the plane of the black hole's equator, or both, or if they are significantly misaligned, would that just not lead to a well-formed disk to begin with.  

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## 1 answers

### Answer by username_2 on 2018-07-19. Score: 6 | Accepted answer

Let me give an answer based on my intuitive understanding of the thing...

### Initial conditions

The initial accretion disk movement is defined by the objects falling into it, the black hole's mass and its spin of course.

If you take the situation where a single star falls on a quiet black-hole, the accretion will appear along the orbit of the infalling object.

[![enter image description here](https://i.sstatic.net/opCmx.png)](https://i.sstatic.net/opCmx.png)
Credit: NASA, S. Gezari (The Johns Hopkins University, Baltimore, Md.), A. Rest (Space Telescope Science Institute, Baltimore, Md.), and R. Chornock (Harvard-Smithsonian Center for Astrophysics, Cambridge, Ma.) and live on [youtube](https://www.youtube.com/watch?v=CpaVzOKihBQ)...

### Equilibrium in an active galactic nucleus

Now on the long run, if additional matter is constantly coming in, at first thought I would think

* the accretion disk momentum will be exchanged with the one of the black hole through the [Penrose process](https://en.wikipedia.org/wiki/Penrose_process),
* Infalling matter momentum will reflect the overall host galaxy momentum - especially if the galaxy is a spiral

> **Comments:**
> **username_0**: fyi I have just asked [Has the Penrose process ever been linked to an observed phenomenon in some way?](https://astronomy.stackexchange.com/q/27298/7982)  

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