# Understanding Light from Black Holes

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• kelly0303
In summary, the conversation discusses the phenomenon of circles of light around a black hole, which were observed in both simulations and a real image of a black hole. The light is forced to move in a circular path due to the strong gravitational field of the black hole. The light is actually coming from an accretion disc, and the appearance of circles is due to gravitational lensing. The structure of what is seen is complex and requires computer calculations. The conversation also mentions specific references to simulations and the real image of a black hole, and provides a link to further explore the topic.
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!

kelly0303 said:
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.

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.

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.

256bits and Dale
PeterDonis said:
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.

256bits said:
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!

kelly0303 said:
Any simulation of a black hole

kelly0303 said:
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.

## 1. What is a black hole?

A black hole is a region in space where the gravitational pull is so strong that nothing, including light, can escape from it. This is due to the extreme curvature of space and time caused by a massive object collapsing in on itself.

## 2. How do black holes affect light?

Black holes have a strong gravitational pull that can bend and distort the path of light. This effect is known as gravitational lensing and it can cause the light from distant objects to appear distorted or even magnified.

## 3. Can we see light from inside a black hole?

No, we cannot see light from inside a black hole because the intense gravitational pull prevents light from escaping. However, we can observe the effects of black holes on surrounding matter and light.

## 4. How does light behave near a black hole?

Near a black hole, light can behave in unusual ways due to the extreme gravitational forces. It can be bent, stretched, and even trapped in orbit around the black hole. This can create unique visual effects and distortions.

## 5. Why is understanding light from black holes important?

Studying light from black holes can provide valuable insights into the nature of gravity, space, and time. It can also help us understand the formation and evolution of galaxies and the role of black holes in the universe. Additionally, it can aid in the development of new technologies and advancements in our understanding of physics.

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