Why do black holes light up when feeding from a star?

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Offline thedoc

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Robert Watson asked the Naked Scientists:
It's often said that, "Nothing can escape a black hole; not even light". Given this, how is it that black holes light up when "feeding" from a star?

If light cannot escape, we would not be able to see it feeding as the light would be pulled into the black hole. Not radiate out away from the black hole as it must be if we can see it.

Can you please explain this for me?

Robert Watson

What do you think?
« Last Edit: 18/03/2014 17:30:01 by _system »


Offline percepts

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Re: Why do black holes light up when feeding from a star?
« Reply #1 on: 20/03/2014 22:12:59 »
becasue what we see is the breakup of matter due to the massive gravitational difference across the matters width/length and resulting emissions as it's sucked into the black hole before it goes past the blackhole event horizon. So what you are seeing is not coming from the blackhole itself but from what is just about to be sucked into it past the point of no return.


Offline Soul Surfer

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Re: Why do black holes light up when feeding from a star?
« Reply #2 on: 20/03/2014 23:51:31 »
Black holes are in fact very difficult to fall into because they are so small.  about one mile across for  every solar mass that they contain so a typical stellar mass black hole is around 10 miles across.  The conservation of angular momentum means that falling towards a black hole unless an object is headed precisely towards it it will swing round it in a hyperbolic orbit and go  away. 

Even if a the centre of a gas cloud or star is headed precisely towards the hole most of the rest of the gas cloud or star would not be and so would miss it and go into would be compressed and heated and then distorted by the angular momentum and would get be very hot.  The orbital velocity of material going round a black hole approaches the velocity of light before the event horizon is reached so this will radiate away about half of the gravitational energy gained during falling in. 

In fact "feeding" a black hole with gas is the most efficient source of energy possible,  because it releases about 50% of the mass energy of the material.
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Offline DanielB

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Re: Why do black holes light up when feeding from a star?
« Reply #3 on: 28/03/2014 19:13:29 »
It would be a two fold action. Compression Fusion that turns into Compression Fission,, The free protons and neutrons, breaking down into the alpha and beta particles, they would deterate rapidly.    And would close the door,, with the gamma rays,, that would be generated.   

They have already done a gamma ray analaysis, and that was the only energy they were able to see so far. 

They measured the surface speed of a black hole,, and that shows a few things.

1.  Surface speed,, 345,000,000 mph,, half the speed of light. 

Every object that is spherical in our universe, are layered into cores,,with the inner core being of molten ,(iron) as in  the earths.   But they are layerd. 

If the inner core,, of the black hole, roates,, just twice as fast,, in hyper gravity,, you have matter moving at the speed of light,, held by the boundries of gravity. 

Question rises.   at 3/4 the speed of light,, whiich even if the core,, only rotated,, just a bit faster than it does now.  (Time dialation )  Hawking radiation would have to take that into account know,, as time dialation,, would be present.

Matter now at the speed of light,, the energy transer of heat, through kinetic energy to the matters core.   With matter at such a intense heat,, and moving at those kind of speeds, wow.  But then again,, gravity,, is all you need.  Or in this case Hyper Gravity. 

Singularity, matter transfering to energy under the force of Hyper gravity.   

Boost the heat factor,, And matter, molten into liquid,, where fusion and fission are taking place.  As the compressoin waves,, fuse atoms together,, pressing them down,, where the fission is taking place.  (recycling our universe).

A black hole would since its gravity,, and matter,,a structural layer
Outter crust, compressoin zone, convection zone, radiation zone. 

Does kind of explain,, since black holes emit gamma rays,, that when new matter is being brought into it,, that it would build up energy,, and release it that fast, as the alpha and beta particles came out,, and then,, the gamma rays..  And burst,, in both directions out of it's north and south poles,, because on a black hole,,it's still it's weakest point of gravity.  And this may explain why they see the gamma ray burst daily,, with our scopes.   After all,, every black hole that builds up the energy.

Side note:  Black holes come in various sizes.  from roughly 20 miles across,, to ours,, 15,000,000 miles wide,, to Andromida's 32,000,000 miles wide..  WIth larger ones out there as well.

I hope this gives you a idea of how,, and why they eject through their poles with gamma ray burst.  It's the result of nuclear fission 

(it's the theory I have just completed, but stays with in the laws of physics,, with all applications of gravity).