Replies

At any rate, I’m probably referencing artistic license from depictions I’ve seen over the years. It would be hard for Hollywood to show a black hole on film if there wasn’t some light to differentiate the blackness from other blackness.

you sort of answered your own question. That's Hollywood!

Black holes are totally devoid of light. The only way I know they can be detected is by the erratic movement of mass around one, or once suspected a massive escape of Gamma Rays. I'm certainly not an expert but was always interested in cosmology.

I suspect that artists in both film and print used a lighter ring on the exterior to give us a reference point.

Black holes are completely invisible themselves, as any light that passes the event horizon is completely consumed. That said, in reality, black holes are usually blazing with light, because as matter falls towards a black hole, it is accelerated and compressed by gravitic forces. As that matter heats up it begins to release light as energy, eventually running through the visible spectrum, and then on up into x-rays.

So the accretion disk around a black hole is ridiculously bright.

Now, if the black hole really was out in space with no matter falling in, it would still be really bright because of the material it ate before. Imagine a photon with just enough energy to stay above the event horizon. It slowly, slowly circles outward until it reaches a point where it can move away from the black hole, giving the hole a slow, rosy glow for millions of years after the last matter fell in.

Finally, if it ran out of that glow, it would still be visible by the massive distortions it causes in light, bending and lensing the light from behind it, and even the light coming from the viewer could be wrapped around the event horizon, coming back to create a sort of mirror image sphere shape, with distorted lens-like properties around it.

There’s a few pictures and more information here: http://www.universetoday.com/74462/what-does-a-black-hole-look-like/

Light that passes near a black hole will be diverted by the gravity, any rotation. Some light will be diverted all the way about. A rotating black hole can add energy to the diverted light and literally send it all the way around. But there will be a sort of ring effect visible from some distance even without rotation. This diversion caused by the gravitational effects and the deformation of the space time can result in all sorts of oddities, including the appearance of the universe "covering up" the black hole, strange changes in the apparent size, or even more bizarre things if the rotating object is distorted by it's rotation. There are models of the visual effects - sometimes reflected in the movies.

Of Course this is all theoretic. Getting close enough to see these effects is very dangerous. Rotating black holes can energize beams of particles and/or radiation that could vaporize the solar system at interstellar distances. Astronomers detect these things and we infer there are black holes at the roots. Astrophysics is not quite certain on the consequences of merging black holes, or the bizarre spacetime distortion caused by a cluster of the things. So I can imagine there's plenty happening that we can't even begin to imagine.