Objects between us and a black hole

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kmarinas86

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If you were to put an object in front of a really large black hole, would the light eminating from this object heading nearly towards us be "peeled" away from us (due to the gravity of the black hole)? And if so, would this "peeling" away cause the object to appear smaller and dimmer than it really is?
 
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vogon13

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Did you mean to say black hole between object and us? <br /><br />As stated, assuming intervening object not close enough to black hole to get zorched in, there would be no effect. <br /><br />Would help to know what extra object is. Star, planet, etc.. <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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kmarinas86

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<font color="yellow">Did you mean to say black hole between object and us?</font>no...<br /><font color="yellow">As stated, assuming intervening object not close enough to black hole to get zorched in, there would be no effect.</font>ok.<br /><br /><font color="yellow">Would help to know what extra object is. Star, planet, etc..</font><br /><br />It could be anything (even dust if we could see its details), as long as it is emitting or reflecting detectable light. If the mass of a black hole is exceedingly large, would a star or planet in front of it appear smaller and dimmer (even imperceptibly) than it really is due to the bending of light? This is assuming that we can see the star or planet just fine even though it's being torn up.<br /><br />The apparent diameter of the object, I think, would shrink because the light escaping from two opposite ends of the object would bend differently with respect to the gravitational force of the black hole. The idea is that when the black hole pulls on light reaching from both sides of the object, that the image of the object will shrink as it approaches us. The light bends in such a way, I think, such that the image scale is reduced and that the planet or star appears smaller than it really is. If a black hole is of sufficient size, is it possible that even an undectable amount of shrinking in the image of the object would occur?
 
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heyscottie

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Depending on how close to the black hole it is, the light from the object would simply be red-shifted to a greater or lesser degree as the light climbs out of the gravity well.<br /><br />If the object we are looking at is extremely wide, maybe a few thousand light years across, so that all the light from it doesn't reach us in parallel beams, then the effect you mentioned could come into effect. But then that object, or at least its outer limits, would be too far from the black hole for it to make a difference.<br /><br />So I don't think there are any cases where we could observe this effect.
 
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Saiph

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yeah, I think it could do that.<br /><br />However it would have to be an extended object, and we'd have to be able to intercept a significant portion of the light comming from it.<br /><br />As it is we basically only see the light heading straight towards us. This light would only be redshifted by a BH, as it can't be turned around (unless the object was in the BH).<br /><br />It's only the light that's heading slightly to either side of this "direct" light, that will be altered, slightly curved back towards the BH. However at interstellar distances, this light already misses earth (to any significant degree anyway). <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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kmarinas86

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Thanks all.<br /><br />Could you verify also that the diameter would appear to decrease, or it is only the brightness, and not the diameter that decreases? Would putting a black hole behind the star or planet be like putting a concave lens on front of it?<br /><br />http://sol.sci.uop.edu/~jfalward/physics17/chapter12/demagnifier2.jpg<br /><br />edit: Now, I think it would actually increase in diamater, because that's how gravitational lenses are, but what about for objects on front of the graviatational lens... I think they increase in diameter too (I somehow got the concave lens thing in reverse).<br /><br />If applied to my hypothesis of giga large black holes (see below), I think that would decrease angular diameter distance and increase the luminosity distance of distant galaxies substantially - link.<br /><br />Thank you.
 
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glutomoto

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Finally found some stuff by Robert Nemiroff of APOD fame about observer and source being on the same side of the lens, but it is a little different, as he talks about the observer being between the source and the lens.<br /><br />from Nemiroff, R. J., American Journal of Physics, 61, 619 (1993)<br /><blockquote>Another set of Einstein rings is observable when the observer and source are on the same side of the lens. Then, for compact sources such as an ultracompact neutron star, light from behind the observer is able to make a "U-turn" around the neutron star and come back to be visible to the observer.</blockquote><br /><br />VISUAL DISTORTION EFFECTS IN A HIGH GRAVITY ENVIRONMENT<br /><br /> Virtual Trips to Black Holes and Neutron Stars by Robert Nemiroff (Michigan Technological University)<br /><br /><br /><img src="/images/icons/smile.gif" /><br />that was a fun lookup. <div class="Discussion_UserSignature"> </div>
 
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