Is the Matter in a Black Hole's Accretion Disc Entering the BH or Circling It?

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Discussion Overview

The discussion revolves around the nature of matter in a black hole's accretion disk, specifically whether this matter has entered the black hole or is merely circling it. The conversation touches on observational methods for identifying black holes, including the role of accretion disks and the challenges associated with detecting them.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that matter in the accretion disk has not crossed the event horizon and is therefore still visible and orbiting the black hole.
  • Others highlight that accretion disks are commonly used to identify black holes, with quasars being cited as examples of supermassive black holes with accretion disks.
  • It is noted that not all black holes possess accretion disks, and the visibility of these disks can depend on their configuration and size, making them difficult to distinguish from other celestial objects.
  • One participant raises concerns about the reliability of using redshift and light distortion from distant galaxies to identify black holes, suggesting that observational limitations may affect the data collected by telescopes.
  • Another participant mentions the impact of time dilation on the perception of matter that has crossed the event horizon, suggesting that it would appear to be at a standstill to a stationary observer.

Areas of Agreement / Disagreement

Participants express differing views on the visibility and identification of black holes through their accretion disks, with no consensus reached on the implications of these observations or the reliability of the methods discussed.

Contextual Notes

Limitations in observational techniques and the assumptions regarding light reaching observers are noted, particularly concerning the effects of gravitational lensing and the challenges posed by foreground galaxies distorting light from more distant objects.

abhiroop_k
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has the matter in the accretion discs for a black hole entered the BH or is it circling the actual BH?...
 
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The matter has not crossed the event horizon of the black hole. If it had, it would not be visible (nor would it be orbiting).
 
i learned (via some documentary) that a BH can be spotted by observing the distortion caused in the light from distant stars as it isn't visible directly...why isn't the accretion disc used for locating a BH in space?...
 
Accretion disks are much more common ways to identify black holes than is gravitational lensing. For example, quasars, the most distant objects we can see in the constant sky, are accretion disks of supermassive black holes.
 
The simple fact is not all black holes will have accretion disks. Furthermore, depending on the configuration, it may be difficult to spot the accretion disk. The features are generally going to be quite small, so it's not as if you'll be looking in a telescope and seeing a literal disk around a dark object. It will instead appear as a point source, so it's not (at least completely) trivial to say that it's an accretion disk and not a star (Of course it's actually not that hard to differentiate between the two, they have different light profiles in general).
 
abhiroop_k said:
has the matter in the accretion discs for a black hole entered the BH or is it circling the actual BH?...

If the matter had passed through the EH then it would appear to be at a standstill to the reference frame of a stationary observer as the speeds get closer to 'c' aka time dilation.
 
abhiroop_k said:
i learned (via some documentary) that a BH can be spotted by observing the distortion caused in the light from distant stars as it isn't visible directly...why isn't the accretion disc used for locating a BH in space?...

As mentioned by Nabeshin: Not all Black holes are known to have accreting matter.Also going by what you're suggesting if we are to use the accretion disc as a property to discover black holes then that follows upon the assumption that light reaches us but this isn't always the case due to Fraunhofer radiation (I think)


I personally believe that taking the red shift light reaching to us can't be a viable source.Recently I read an article about how much data we have gathered from Hubbles Space telescope yet the uncertainty i.e the number of galaxies observed seems high which is to say that quite often the forehead galaxies distort the incoming light from the distant galaxies,so to get over this issue James webb Telescope shall operate soon.

Regards
ibysaiyan
 
thanks
 

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