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Can You See A Black Hole?

  1. Yes

    2 vote(s)
    20.0%
  2. No

    6 vote(s)
    60.0%
  3. Yes, but only with those really cool 3-D Movie Glasses

    1 vote(s)
    10.0%
  4. I don't know

    1 vote(s)
    10.0%
  1. Mar 17, 2006 #1
    I am just curious as to what the generally accepted ideas are about black holes.
     
  2. jcsd
  3. Mar 17, 2006 #2

    JasonRox

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    I would say no because that would totally contradict what they are saying about black holes.

    The only way to detect them (from what I know) is to find things moving about something that which we can not see, and that observing this, the object must be really massive.
     
  4. Mar 17, 2006 #3

    chroot

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    You can't see the surface of a black hole, of course; it absorbs all light which hits it.

    You can however, see the accretion disk, the ring of in-falling matter which commonly orbits black holes, spiraling inward towards the hole. As material gets closer and closer to the black hole, the tidal forces become more and more severe. The squeezing and stretching generates a lot of heat, and it's common for matter in an accretion disk to be so hot it's glowing in X-rays!

    This is actually how quasars are detected, and quasars are some of the most distant objects known in the universe. Quasars are hypothesized to contain active, supermassive black holes, and we see the intense radiation from their accretion disks billions of light-years away. No other known process can generate such intense radiation.

    - Warren
     
  5. Mar 17, 2006 #4
    :confused: :confused:
    I don't understand what you mean with this option:confused:
     
  6. Mar 18, 2006 #5

    russ_watters

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    That's probably a joke, scott1.

    This depends on what you mean by "see".

    I heard there is work being done on a telescope that can actually see the event horizon of a black hole due to the fact that it would be darker than the surrounding gas/dust: A "hole" in a nebula.
     
  7. Mar 18, 2006 #6

    pervect

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    It would take rather special circumstances to see a black hole.

    One possibility is that the black hole could come between you and a star, in which case you might see Einstein rings.

    Another interesting possiblity is that if you had a really bright light (or a laser beam), you could also "see" light bent through an angle of 360, 720, 1080, etc. degrees if you shone the light at the black hole. But it would probably be difficult to get a light bright enough (or a laser with enough intensity) to actually pull this trick off.

    It would be much more likely that you would see the accretion disk around the hole, as others have remarked.
     
  8. Mar 18, 2006 #7

    George Jones

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    To me, this seems very implausible. Betelgeuse is a close supergiant star whose disk astronomers are just able to resolve. If my calculations are correct, the disk of the supermassive black hole at the centre of our galaxy subtends an anlgle much smaller than the disk of Betelgeuse. Also, the optical image of this supermassive black hole would be completely blocked by dust and other stuff. The situation for a 10 solar mass black hole formed from stellar collapse seems even more hopeless.

    Regards,
    George
     
  9. Mar 18, 2006 #8

    George Jones

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    Can a black hole be seen?

    Yes, if the black hole is small enough.

    Regards,
    George
     
  10. Mar 18, 2006 #9
    Can you explain why if a black hole is small enough it can be seen?
     
  11. Mar 18, 2006 #10

    SpaceTiger

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    Smaller black holes emit more Hawking radiation, which is probably the closest one gets to directly "seeing" the black hole. If you include radiation from accretion, however, the big black holes have the potential to be much brighter (due to a larger Eddington luminosity).
     
  12. Mar 21, 2006 #11
    i don't think that a human eye can see xrays or hawking radiation
     
  13. Mar 21, 2006 #12
    You can always see a black hole by the gravitational distortion that it causes to the background of stars even if it is not accreting or so small that it radiates visible light but because they are so small (stellar mass holes are only a few Km across) you have to be very close before you could resolve it as a disc with the naked eye even monster holes in the middle of galaxies are only as big as the solar system so again you probably have to be within a light year or so to see a disc.

    I have seen simulations of this on video but don't know if any are available on the web
     
  14. Mar 21, 2006 #13

    Hurkyl

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    You can see hawking radiation if it's in the visible spectrum. :tongue:
     
  15. Mar 22, 2006 #14
    This is a purely philosophical question. Can you see blackness? Is seeing actually detecting light with your eyes, or more generally, taking in information with your eyes. It all depends on how you want to define it, making this thread unscientific and pointless.
     
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