shouldn't a black hole have a super bright halo?

[bwanaaa]

Up to some distance from the center of a black hole, light is swallowed up. yes? This is called the event horizon. At the event horizon, light is captured and enters a stable orbit around the black hole. Over time, the amount of light orbiting the black hole should increase as it captures more and more. Of course, an observer would never see this because the light never leaves orbit to go to the observer's eye. However, recent information suggests that some light escapes this orbit. As I recall (and again the source escapes me) it was a theoretical physics type of thing-not an actual observed phenomenon-but a calculated quantum event. If ligh (or any other particle escapes the black hole, it would exit and travel tangentially to its escape point. An observer would therefore see the black hole as a bright ring-where all the light is escaping. From a theoretical standpoint, it makes sense that some light might escape-collisions of photons with particles at the event horizon would result in scattering. Although most of the scattered photons would be swallowed up, some would escape. As the captured light in the event horizon increases with black hole age, the amount of scattering should increase, and therefore the hole's halo should get brighter. Thus a black hole should really be called a 'haloed black hole'. (Ahem, hallowed black hole? a black holy? a black halo?) Have we ever seen any halo objects?

 

[KIAman]

As far as I know, unless there is some way to make light faster than the speed of light, this is impossible. Collisions, explosions, detonations, scattering, etc. won't cause light to go faster than the speed of light.

 

[bsobel]

Originally posted by: bwanaaa
Up to some distance from the center of a black hole, light is swallowed up. yes? This is called the event horizon. At the event horizon, light is captured and enters a stable orbit around the black hole. Over time, the amount of light orbiting the black hole should increase as it captures more and more. Of course, an observer would never see this because the light never leaves orbit to go to the observer's eye. However, recent information suggests that some light escapes this orbit. As I recall (and again the source escapes me) it was a theoretical physics type of thing-not an actual observed phenomenon-but a calculated quantum event. If ligh (or any other particle escapes the black hole, it would exit and travel tangentially to its escape point. An observer would therefore see the black hole as a bright ring-where all the light is escaping. From a theoretical standpoint, it makes sense that some light might escape-collisions of photons with particles at the event horizon would result in scattering. Although most of the scattered photons would be swallowed up, some would escape. As the captured light in the event horizon increases with black hole age, the amount of scattering should increase, and therefore the hole's halo should get brighter. Thus a black hole should really be called a 'haloed black hole'. (Ahem, hallowed black hole? a black holy? a black halo?) Have we ever seen any halo objects?

This is pretty much all wrong. Light isn't 'swalloed up', it simply can never reach the event horizon due to the bending of space/time around the singularity. The event horizon simply is the point where light can escape or not, it doesnt define a stable orbit for protons.

Proton colissions don't accelerate the proton's, no additoinal energy is created so they can't get 'bumped out' and suddenly escape.

As for the quantum effects your discussing, google Hawking radiation.

 

[bwanaaa]

ok so i didnt use the right jargon. yes i understand that it is spacetime that is warped and if you were 'riding on a photon and looked around' it would appear to be going in a straight line. But consider these three scenarios:
1)incident photons directed at the black hole would fall into the black hole.
2)photons passing near the black hole but away from the event horizon would be refracted.
3)photons falling tangential to the event horizon would be continually refracted by the event horizon and appear to an outside observer as orbiting the black hole.

i did not suggest that photons collide with photons(I assune that's what you were trying to argue with) Rather, I was suggesting that photons at the event horizon could be scatterred by matter at the event horizon and travel away from the event horizon. That would result in light escaping from the event horizon. if there is a boundary where where light can or cannot escape, then why cant PHOTONS (not protons) 'orbit' at that location.

 

[KIAman]

Originally posted by: bwanaaa
ok so i didnt use the right jargon. yes i understand that it is spacetime that is warped and if you were 'riding on a photon and looked around' it would appear to be going in a straight line. But consider these three scenarios:
1)incident photons directed at the black hole would fall into the black hole.
2)photons passing near the black hole but away from the event horizon would be refracted.
3)photons falling tangential to the event horizon would be continually refracted by the event horizon and appear to an outside observer as orbiting the black hole.

i did not suggest that photons collide with photons(I assune that's what you were trying to argue with) Rather, I was suggesting that photons at the event horizon could be scatterred by matter at the event horizon and travel away from the event horizon. That would result in light escaping from the event horizon. if there is a boundary where where light can or cannot escape, then why cant PHOTONS (not protons) 'orbit' at that location.

Even if the photons get close to the event horizon and somehow gets bounced out, why would that create a halo? This seems no different than bending of light. There is no reason why light would slow down and amass near the event horizon, then release all at once to make a halo. The light never slows down (nor speeds up).

 

[dananski]

I think I see what you're getting at - you are saying that if the photons are scattered at a perfect tangent to their 'orbit' around the black hole (assumed spherically symmetric) then the only particles that would reach the observers a great distance away would be the ones from the outline of the Schwarzschild radius (a circle, or "halo"). Unfortunately, I would imagine that if such a scattering were possible, it would not be at a perfect tangent like this and the photons would in any case simply spiral outwards such that their emergent angle could be anything. I don't know if anyone has successfully done photon-matter scattering calculations in a Schwarzschild metric, but when you start to combine black holes and quantum field theory, things tend to get a bit impossible.

The effect you are proposing would also require impossible starting conditions as the photons would have to be 'orbiting' at an incredibly precise radius - any further either towards or away from the singularity would mean they quickly fall away or towards it respectively. This is called an unstable equilibrium - it's like balancing your pencil on the sharpened nib, only in a gravitational field that is so strong it can bend light round in circles! This would mean that your photons will not be there for long unless perfectly aligned, and then they would be in the wrong place as soon as the black hole gained any more mass.

 

[bwanaaa]

who said anything about light slowing down or speeding up? i am trying to say there are 2 processes going on:
1) gravitaional lensing of light near the event horizon
2) capture and emission of light at the event horizon
Some light should be captured and accumulated, not absorbed because it hasnt collided with matter yet. the light is in orbit at the event horizon because spacetime is so curved there. it's only the photon that hits the event horizon tangentially. the analogy might be an asteroid that enters earth orbit. except photons have a fixed velocity so there is only one entry angle that will allow them to enter orbit. Over time, these are the only photons that accumulate. What might then happen if such an orbiting photon collides with matter? It would be scattered. some photons get scattered into the black hole. some get scattered out.

I just do not understand how you could theoretically explain the jets of radiation that exit like fountains off of the poles of a quasar when a black hole is 'feeding' i would expect the radiation to exit symmetrically everywhere. the only 'extra' brightness should result from lensing, a brighter rim. that's what i mean by halo.

 

[KIAman]

I think you are missing the point. If a photon has reached the event horizon close enough to induce an orbit, it is already stuck. The space-time is already so far bent that it exceeds the speed of light. The only way for that photon to ever "escape" from that orbit is to exceed the speed of light. I understand there are a lot of strange and wonderful quantum forces going on but no matter what imagination and theories cook up, the cosmic speed limit of light cannot be broken.

Let's use your asteroid as an example.

An asteroid enters a perfect orbit around Earth due to the perfect entry angle. Now, let's assume this process happens a lot and now we've got trillions of asteroids spinning around earth. Now, the asteroids start to collide and interact with other things in orbit and some asteroids fall towards Earth and others leave orbit completely.

Sounds like a good analogy. But, the asteroids which left orbit would have to increase their relative tangential speed to exceed the escape velocity of the Earth. Light does not have that luxury. What if you change the angle to point outwards? There is now not enough speed to keep the photon from falling inwards because it's angular speed has decreased by changing it's angle outwards.

Does not matter what mechanics you could think of near the event horizon, nothing will make the light exceed it's speed. Lensing is a completely different phenomena but you only "see" the object that is behind the black hole, a star, for example. Unless that star looks like a halo, the light you see from lensing won't look like a halo.

A particle may capture and re-emit light, yes. Have that particle go .99c and have it emit a photon in the direction of travel. That photon will still only go 1c.

You might not see the connection between the speed of light and what you are proposing, but there it is.

 

[Biftheunderstudy]

Ah, finally the real question behind these posts. For the scattering of photons near the event horizon KIAman is right, also if the central black hole is feeding the event horizon is getting bigger effectively eating all those orbiting photons. There are some other effects to worry about, like the fact that the central black hole is most certainly rotating. Look up something called an ergoshpere -- rotating black holes are a bit tricky.

Astrophysical jets are not understood very well right now. This is actually at least tangentially related to my thesis. The most likely candidate for jet formation is the following scenario.
Around the black hole is a large accretion disk, through this disk are threaded magnetic fields. The hot plasma drags the field around and winds it up, you get a spiral magnetic field perpendicular to the disk -- through some more arguments you can say it has to be at the poles. Next, charged particles are accelerated to very high speeds along these field lines and emit synchrotron emission.

Thats sort of jets in a nutshell, there is a lot more to it.

 

[bwanaaa]

thank you kiaman for that clear explanation. i get it. i see your point about scattering-thank you. the net result is that there will never be scattering at that location, just absorption of light. likewise, photons could not be scattered into the black hole either. the only way to conceivably allow scattering is if there are fluctuations in the event horizon boundary-that way a photon may suddenly find itself outside the boundary and then take off tangentially-> this would give a bright rimmed black hole (hmmm,rimming a black hole?) no matter where you were in space looking at the black hole.

regarding jets, i appreciate the explanation. therefore jets are forming outside the event horizon. some material crashing towards the black hole follows the field lines toward the magnetic poles. at the poles it all crashes together-some of the stuff jets into the black hole (which we dont see) and some stuff shoots outwards.

 

[JTsyo]

shouldn't a black hole have a super bright halo?

There is. It's called an accretion disk, it's just that for black holes the radiation is tin the x-ray frequency. Obviously it's not made of escaping light but material being compressed by immense gravity.

 

[dinkumthinkum]

In the sum-over-histories formulation of QED, photons are able to travel at super- (and sub-) luminary velocities. The observed "usual" behavior is the result after these possible (but with differing amplitude) paths cancel each other out. But what is the implication of this in a curved space-time?

 

[aj654987]

Keep in mind that spacetime is bent around the black hole in all planes, so lets say that the light would all stick around at the edge of the event horizon (which it wont) then you would have a big glowing ball not a halo. In other words the event horizon is a 3 dimensional boundary or sphere.

The wireframe diagrams showing curved space in one plane to demonstrate the bending of space as calculated by general relativity are probably what is giving you the halo idea. They just show a 2d plane being bent so that the picture is easy to read, but as gravity works in all 3 dimensions, the event horizon would be a spherical boundary.