Interesting thought about black holes

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Discussion Overview

The discussion revolves around the visibility of black holes and the methods used to detect them, including the phenomena surrounding their event horizons. Participants explore concepts related to accretion, radiation, and the challenges of direct observation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that while we cannot see objects entering a black hole, we might observe the matter surrounding it, particularly near the event horizon.
  • Others note that astronomers detect black holes primarily through the X-ray radiation emitted by gases being accreted, which is a common method for locating them.
  • One participant emphasizes that the observable effects, such as redshifting and time dilation, may render signals from near the event horizon unobservable before they can be detected.
  • There is a claim that direct detection of black holes is impossible, but indirect evidence through accretion discs and gravitational effects in binary systems is compelling.
  • Some participants express skepticism about the portrayal of black holes in media, questioning the accuracy of representations in television shows.
  • A later reply mentions the potential for imaging the black hole at the center of the galaxy in the near future, referencing scientific articles and studies.

Areas of Agreement / Disagreement

Participants express a mix of agreement and disagreement regarding the visibility of black holes and the methods of detection. While some acknowledge the existence of indirect evidence, others remain uncertain about the portrayal of black holes in popular media.

Contextual Notes

Participants reference various detection methods and the limitations of current observational technology, but there is no consensus on the implications of these methods or the accuracy of media representations.

Who May Find This Useful

Readers interested in astrophysics, black hole research, and the methods of astronomical observation may find this discussion relevant.

iRaid
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Well since we will never see something go into a black hole, won't we see everything the black hole tries to swallow around it? So wouldn't it be possible to see a black hole since a bunch of things would be around the event horizon.

Answers are appreciated.
 
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Thats pretty much how astronomers spot black holes. The gasses that are being swallowed by the hole emmit X-ray radiation which is mainly what they look when searching for black holes.
 
Sakha said:
Thats pretty much how astronomers spot black holes. The gasses that are being swallowed by the hole emmit X-ray radiation which is mainly what they look when searching for black holes.

Yes, but this doesn't have anything to do with time dilation. This is simply normal matter accreting onto the black hole. By the time things start redshifting and slowing down near the event horizon, it's likely that these signals would no longer be observable.
 
I was pretty sure they haven't spotted black holes from the show I saw on tv..
 
Direct detection of black holes is, by definition, basically impossible. Detection of accretion discs radiationg unbelievable amounts of high energy radiation is more than possible [e.g., quasars] Black holes can also be detected by gravitational effects in binary systems and lensing. While not direct detection, the evidence is fairly compelling.
 
Hmm tv shows like to trick me I guess :p
 
iRaid said:
Well since we will never see something go into a black hole, won't we see everything the black hole tries to swallow around it? So wouldn't it be possible to see a black hole since a bunch of things would be around the event horizon.

Answers are appreciated.

There is a good chance that, within a decade or so, we should be able to "image" in this way the astrophysical black hole at the centre of our galaxy. See

http://www.scientificamerican.com/article.cfm?id=portrait-of-a-black-hole

http://arxiv.org/abs/astro-ph/0607279.
 

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