Understanding Light from Black Holes

[kelly0303]

Hello! I am a bit confused about the circles of light around a black hole, that were present both in simulations and in that image of a real black hole. I understand that the gravitational field is so strong around the black hole that the light is forced to move in a circular path around (from our point of view) around the black hole. But i am not sure how can we see that. If the light moves in a circle, doesn't it mean that you must be on the edge of the circle to see it? What I mean is, if I stay at a distance from the circle, in order to see it, the light should come towards me, but that would mean that it doesn't move in a circle anymore. So what do we exactly see there? Thank you!

 

[PeterDonis]

I am a bit confused about the circles of light around a black hole, that were present both in simulations and in that image of a real black hole.

What simulations and what image? Please give specific references.

 

[256bits]

Light that is passing by the black hole farther out than the "light that circles around a black hole" is what you see.
Gravitational lensing is what you need to research.

 

[Ibix]

The light is coming from an accretion disc, matter spiralling down into the black hole and heating itself by friction. We're looking at it at an angle, though, and the gravity of the black hole is strong enough so that light coming from the far side of the accretion disc gets bent around the black hole and reaches us. So you see a ring around the hole because you see light that's gone "over" the hole - loosely speaking, a bit like a ball thrown over a wall.

The exact structure of what you see is rather complex and requires computer number crunching, but that's the gist of it.

 

[kelly0303]

What simulations and what image? Please give specific references.

Any simulation of a black hole and I am pretty sure there is only one image made of a real black hole.

 

[kelly0303]

Light that is passing by the black hole farther out than the "light that circles around a black hole" is what you see.
Gravitational lensing is what you need to research.

Thank you so much!

 

[PeterDonis]

Any simulation of a black hole

Have you actually looked at any? If so, please give links.

I am pretty sure there is only one image made of a real black hole.

There is one that made the news recently, yes. But there are lots of versions of the image online. Which particular one did you look at? Please give a link.

 

[vanhees71]

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