From neutron star to Black Hole...........?

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Ethos

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From neutron star to Black Hole...........?
« on: 09/04/2009 05:08:44 »
Maybe one of you fellows can answer a question for me?

Let's imagine that we have the means to experiment with a neutron star. Parking ourselves close enough for our experiment, we aim a neutron gun at the star and begin to inject neutrons into it at a controled rate. This experiment is being preformed with the goal of finding out exactly how much mass needs to accumulate within the body before it becomes a Black Hole. Keeping in mind that care is taken not to add neutrons so fast that it's equilibrium is upset resulting in an explosive event.

My question is: What is the least amount of mass we must accumulate within this neutron star to transform it into a Black Hole?

I have a book by John Archibald Wheeler that draws conclusions about Black Hole formation but he does not investigate this particular method for Black Hole creation. I believe the method I've purposed would create a Black Hole with the least amount of perturbation, and the resulting figures for the mass and compaction could be viewed as a universal constant of sorts. This threshold, between our universe and what lies beyond within the Black Hole, should be an important commological plateau that must surely hold much significance.....................Ethos

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Offline Raghavendra

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« Reply #1 on: 09/04/2009 07:49:20 »
I will answer this question?

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Offline Soul Surfer

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« Reply #2 on: 10/04/2009 19:37:07 »
It is a good deal less than the mass of a typical neutron star but probably more than ten percent of the mass of the neutron star exactly how much depends on the mass of the neutron star which is not totally fixed. The collapse process may go through a slightly more dense stable state called a quark star before becoming a black hole where the neutrond collpse and individual quarks have asymptototic freedom.  Neutron stars are quite close to being black holes and cause very significant distortions to space time
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Offline LeeE

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« Reply #3 on: 10/04/2009 21:33:11 »
I don't think that simply adding mass to a neutron star would work.

In adding mass, you're just adding to the quantity of matter but for a black hole to form you need to increase the density.  Unless there is an upper limit to the size that neutrons stars can achieve (not to be confused with the maximum size of a neutron star that can be created) you're just going to create a bigger neutron star.

To turn a neutron star in to a black hole you'd need to compress it, not just make it bigger.

With a small enough neutron star though, you might be able to compress it explosively, in a similar sort of manner to the way that fission bomb sub-critical mass cores are compressed to a critical mass, to get it dense enough.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Ethos

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« Reply #4 on: 11/04/2009 01:13:23 »
I don't think that simply adding mass to a neutron star would work.

To turn a neutron star in to a black hole you'd need to compress it, not just make it bigger.

Wouldn't compression come as a result of the added gravitational attraction? That is, if I understand correctly, the driving force behind all Black Hole formation anyway..........Ethos

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Offline Vern

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« Reply #5 on: 11/04/2009 23:43:55 »
Quote from: LeeE
I don't think that simply adding mass to a neutron star would work.
This should be solvable. We know the density of neutron stars. There should be a way to compute a size where that density would not allow light to escape. That would be a black hole, in effect, however there need not be a singularity at its centre.

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Ethos

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« Reply #6 on: 12/04/2009 02:29:46 »
Quote from: LeeE
I don't think that simply adding mass to a neutron star would work.
This should be solvable. We know the density of neutron stars. There should be a way to compute a size where that density would not allow light to escape. That would be a black hole, in effect, however there need not be a singularity at its centre.

Astute observation Vern, I hadn't considered that particular twist.

When this threshold of mass density is achieved, I believe we could establish a new natural constant of nature. In some respects, this new ground state of Black Hole structure might represent an entity as basic as the electorn itself. One might argue that this structure is unique enough to refer to it as a single particle. I realize that statment takes a leap of imagination but, it may be interesting to examine this possibility. If we can think in terms of the electron being the smallest unit of mass in the natural world, this new structure might be viewed as the largest. Everything which lies between these two states is everything we understand about matter. Might be very interesting to know the results for this following equation:

Let me equal the mass of the electron
Let Mo equal the mass of our hypothetical neutron star

I would like to know the answer to (Mo/me)

......................Ethos

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Offline Mr. Scientist

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From neutron star to Black Hole...........?
« Reply #7 on: 12/04/2009 02:39:50 »
Maybe one of you fellows can answer a question for me?

Let's imagine that we have the means to experiment with a neutron star. Parking ourselves close enough for our experiment, we aim a neutron gun at the star and begin to inject neutrons into it at a controled rate. This experiment is being preformed with the goal of finding out exactly how much mass needs to accumulate within the body before it becomes a Black Hole. Keeping in mind that care is taken not to add neutrons so fast that it's equilibrium is upset resulting in an explosive event.

My question is: What is the least amount of mass we must accumulate within this neutron star to transform it into a Black Hole?

I have a book by John Archibald Wheeler that draws conclusions about Black Hole formation but he does not investigate this particular method for Black Hole creation. I believe the method I've purposed would create a Black Hole with the least amount of perturbation, and the resulting figures for the mass and compaction could be viewed as a universal constant of sorts. This threshold, between our universe and what lies beyond within the Black Hole, should be an important commological plateau that must surely hold much significance.....................Ethos

Even if you fired the particles at the neutron star, mankind will probably have died out before seeing anything spectacular. Needless to say also, a rule called the uncertainty between time and energy given as \Delta E \Delta t \approx \hbar. This meddles up any exact calculation on the mass as well, simply because according to this equation, it would be, indeterminable.
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Offline Vern

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« Reply #8 on: 12/04/2009 16:35:23 »
Quote from: Ethos
Let me equal the mass of the electron
Let Mo equal the mass of our hypothetical neutron star

I would like to know the answer to (Mo/me)

......................Ethos
Yes; that would be interesting. There should be such a size for a neutron star. It might be possible even for ordinary matter, but since we don't observe any such monsters, there is probably a limiting factor on the size of objects. My guess is the limiting factor would be gravity.

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Offline JP

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« Reply #9 on: 13/04/2009 02:38:19 »
Quote from: LeeE
I don't think that simply adding mass to a neutron star would work.
This should be solvable. We know the density of neutron stars. There should be a way to compute a size where that density would not allow light to escape. That would be a black hole, in effect, however there need not be a singularity at its centre.


We can assume a basic model of a non-rotating neutron star, made of matter of density ρ.  A non-rotating object will collapse into a black hole if it falls within its own Schwarzschild radius.  The equation for this radius is:

rs=K m,

where K=2Gc-2 is a constant that includes on the speed of light and the gravitational constant and m is the mass of the object.  Now, there's a simple relation between mass and density, (and we'll assume a spherical object):
m=4/3π r3ρ .

Plugging this into the mass above...

rs=[3/(4Kρπ)]1/2

I plugged in some numbers from wikipedia for the density of a neutron star 5x1017kg/m3, and got

rs≈18 km.


Edit: Fixed the error LeeE pointed out.
« Last Edit: 15/04/2009 01:11:11 by jpetruccelli »

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Offline JP

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« Reply #10 on: 13/04/2009 02:42:32 »
And I think this corresponds to somewhere in the ballpark of 6 solar masses for a neutron star of that radius.  All this is a very rough approximation since real neutron stars are likely rotating and not of uniform density.  In fact, we don't even have a good handle on the physics going on inside of neutron stars.

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Ethos

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« Reply #11 on: 13/04/2009 04:00:24 »
  In fact, we don't even have a good handle on the physics going on inside of neutron stars.
Good points jpet...., I suppose one needs to look beyond the neutron star to the possible formation of a quark and gluon star. I think my imagination has reached well beyond our present ability to correctly analyze such objects. Sadly, it may be many years before we can answer the question I presented with the opening of this thread. Nevertheless, I believe the answer to this question should shed much light on the nature of matter................Ethos

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Offline Vern

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« Reply #12 on: 14/04/2009 03:39:32 »
Quote from: jpetruccelli
We can assume a basic model of a non-rotating neutron star, made of matter of density ρ.  A non-rotating object will collapse into a black hole if it falls within its own Schwarzschild radius.  The equation for this radius is:

rs=K m,
Are we sure about the collapse here? I don't remember a requirement for this. Maybe I missed it, but I didn't realize there was something magical about the Schwarzschild radius that would initiate a collapse into a singularity.

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Offline JP

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« Reply #13 on: 14/04/2009 06:19:25 »
Yes.  The Schwarzschild solution is valid outside of the nonrotating spherically symmetric object.  If the object falls within its Schwarzschild radius, then there is a region of space (within the radius, but outside the object) where the only valid space-time paths are pointed towards the center of the object.  This should ensure the collapse of the object.

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Offline LeeE

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« Reply #14 on: 15/04/2009 00:51:43 »
Quote from: LeeE
I don't think that simply adding mass to a neutron star would work.
This should be solvable. We know the density of neutron stars. There should be a way to compute a size where that density would not allow light to escape. That would be a black hole, in effect, however there need not be a singularity at its centre.


We can assume a basic model of a non-rotating neutron star, made of matter of density ρ.  A non-rotating object will collapse into a black hole if it falls within its own Schwarzschild radius.  The equation for this radius is:

rs=K m,

where K=2Gc-2 is a constant that includes on the speed of light and the gravitational constant and m is the mass of the object.  Now, there's a simple relation between mass and density, (and we'll assume a spherical object):
m=4/3π r3.

Plugging this into the mass above...

rs=[3/(4Kρπ)]1/2

I plugged in some numbers from wikipedia for the density of a neutron star 5x1017kg/m3, and got

rs≈18 km.


Umm...

Quote
m=4/3π r3

shouldn't that be V=4/3π r3?

I can't see how you've arrived at rs≈18 km without specifying the mass anywhere.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Ethos

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« Reply #15 on: 15/04/2009 01:05:09 »

I can't see how you've arrived at rs≈18 km without specifying the mass anywhere.
I believe he posted these figures: (5X10^17kg/m^3) If you'll notice, this is where the mass, in kg's, is specified..............Ethos

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Ethos

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« Reply #16 on: 15/04/2009 01:09:32 »
From what I've learned, the equation; r = 2G X m/c^2 represents the calculation for the radius of the schartzchild metric. In truth, you can plug in any figure for the mass in this equation and determine the radius at which it will become a Black Hole.

...................Ethos

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Offline JP

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« Reply #17 on: 15/04/2009 01:10:21 »
Quote
m=4/3π r3

shouldn't that be V=4/3π r3?

I can't see how you've arrived at rs≈18 km without specifying the mass anywhere.

Oops.  I thought I clicked the button to insert a "rho."  That should read

m=4/3πr3ρ (=Volume x Density)

The rest should make sense now, since I used density instead of mass in the calculations.
« Last Edit: 15/04/2009 01:12:08 by jpetruccelli »

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Offline LeeE

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« Reply #18 on: 15/04/2009 20:14:36 »
Quote
m=4/3π r3

shouldn't that be V=4/3π r3?

I can't see how you've arrived at rs≈18 km without specifying the mass anywhere.

Oops.  I thought I clicked the button to insert a "rho."  That should read

m=4/3πr3ρ (=Volume x Density)

The rest should make sense now, since I used density instead of mass in the calculations.

If you're going to use density, you'll still have to specify either the mass or the volume, so in m=4/3πr3ρ don't you still need to specify a value for r?
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline LeeE

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« Reply #19 on: 15/04/2009 20:17:23 »

I can't see how you've arrived at rs≈18 km without specifying the mass anywhere.
I believe he posted these figures: (5X10^17kg/m^3) If you'll notice, this is where the mass, in kg's, is specified..............Ethos

Ethos, that's not specifying a number of kg - all it's saying is that a certain number of kg relates to a corresponding number of cubic metres for a given density.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline JP

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« Reply #20 on: 16/04/2009 06:26:49 »
Quote
m=4/3π r3

shouldn't that be V=4/3π r3?

I can't see how you've arrived at rs≈18 km without specifying the mass anywhere.

Oops.  I thought I clicked the button to insert a "rho."  That should read

m=4/3πr3ρ (=Volume x Density)

The rest should make sense now, since I used density instead of mass in the calculations.

If you're going to use density, you'll still have to specify either the mass or the volume, so in m=4/3πr3ρ don't you still need to specify a value for r?

Ah... if it wasn't clear above, an object becomes a black hole when all its mass lies within the Schwarzschild radius.  I therefore set its radius (in the volume equation) equal to the Schwarzschild radius, which eliminates all my variables except for Schwarzschild radius and density.

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Offline LeeE

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« Reply #21 on: 16/04/2009 16:09:21 »
Ah yes, right - I was being a bit dim there.

It seems that the size limits for neutron star creation are quite limited - between about 1.35 and 2.1 solar masses, and they all seem to have a radius of about 12km (it would seem that the difference in their creation mass is only reflected in their density - I don't know the reason for this)

So for a neutron star to reach a radius of 18km, whilst remaining at the same average density of 4.96e+17, it would have to increase it's mass and volume by about 3.38 times.

In practice though, I suspect it's density would increase a little as mass was added, so it would collapse a little sooner, but the nova that formed the neutron star would have left relatively little matter in the region around the neutron star that could fall in to it, so it could probably only happen to a very old neutron star, or one that was propelled away from it's original location so that it could eventually acquire the extra mass from somewhere else.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline yor_on

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« Reply #22 on: 17/04/2009 11:18:35 »
As far as I understand it, even if we had Neutron stars with a event horizon they still wouldn't be the same as a black hole. " One feature of black holes that should not appear around a neutron star is a last stable orbit. Around a black hole, one finds a minimum radius for the orbit of an object; inside this radius, an object must fall onto the event horizon of the black hole. This effect could only appear around a neutron star if the surface of the neutron star were inside this radius.

This would require a stellar radius that is only 50% larger than the event horizon radius, which is a result not produced by most neutron star theories. If such an object existed, however, it should be easily demonstrated, because the gravitational redshift from a neutron star with a surface at the last stable redshift is a massive 42%.

The gravitation redshift is a direct measure of the ratio of the star's mass to its radius. For this reason, the measurement of redshift is an important measure of the structure of the star, and ultimately of the behavior of the material within the neutron star."

Another reason to why I don't think Neutron stars can have a Event Horizon is that a Neutron Star then will be a 'known entiety' made out of fermions (neutrons and Protons) having a 'rigid' construction inside that star without anywhere for a neutron to decay into a "a proton and an electron, releasing a neutrino and a small amount of energy in the process. This cannot happen to a neutron in a cold neutron star because the proton would have nowhere to go; the proton must go into an energy state that at most contains only one proton, but no such state is available.

Conversely, the inverse process, the absorption of an electron by a proton to create a neutron, cannot occur because all of the available neutron energy states are filled. This is why the number of protons and neutrons in a cold neutron star are nearly identical."
http://www.astrophysicsspectator.com/topics/degeneracy/NeutronStarSize.html

Also "the neutron and proton are nearly equal in size. This is because, at the tiny distances in the nucleus, the strong nuclear force is much stronger than any of the others. Under just the strong force, protons and neutrons are effectively the same particle; this is an example of something called "isospin symmetry." And the size of them is calculated to be about a Femtometer (1 fm = 10^{-15} m = 0.000000000000001 m).

So if the definition for a black hole is a place where nothing (information) can be reflected once passed the Event Horizon, remembering that a neutron star is defined by the Pauli exclusion principle stating that there can't be two any fermions occupying the same quantum state simultaneously, then one of those definitions should be wrong? http://en.wikipedia.org/wiki/Pauli_exclusion_principle#Astrophysics_and_the_Pauli_principle

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That is as we suddenly would have 'information' on a Black hole as we would know the structure inside that Event Horizon. Also, how can it be able to have both a event horizon that LeeE defines as where 'time' stops, as well as then being equivalent to 'c', and still with 'ordinary fermions' being the cause of it?

But you will still be able to differ between a Neutron star and a Black Hole. "If such an object existed, however, it should be easily demonstrated, because the gravitational redshift from a neutron star with a surface at the last stable redshift is a massive 42%."

Also, if there isn't any such phenomena as Neutron stars with a event horizon then their particles (Neutrons and Protons) size together with the Pauli Exclusion Principle should help define a possible 'limit'  from where fermions might break down into 'real' Black Holes as they pass this limiting size?

 
« Last Edit: 17/04/2009 11:46:06 by yor_on »
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Offline Vern

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« Reply #23 on: 17/04/2009 17:11:15 »
If I am understanding all this correctly, it seems that to become a black hole, a neutron star must annihilate all of its matter into a quark-gluon soup, which then can collapse into a black hole. Such an event should not go unnoticed because it would produce Quasar-like energy levels.

Surely, neutron stars continuously gain mass from space debris and by cannibalizing near-by neighbours. Some should have become black holes if they existed since the universe was young.   

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« Reply #24 on: 17/04/2009 21:20:14 »
I don't know Vern:) Nothing new with that, is there ::))
I'm not even sure in believing that a Neutron star gives us a 'limit' for where a Black hole may appear? To me it seems like a Black hole will be working from a state where fermions 'disappear' into something alike 'bosons'  for it to make sense?? And then those 'Bosons' will be 'compressed' or 'superimposed' if you like into a 'dimensionless' point inside that Black hole. And looking at it that way a Black hole seems more like a 'hole' in spacetime than anything else to me?

--
Looking on it like that it makes sense in believing that Black holes is formed at the beginning of spacetime, as we can't really have 'super vacuum cleaners' eating up all 'matter/mass'. that as if matter never reaches that 'dimensionless' point 'spacetime' will have a certain density?? Otherwise it seems to me like the universe would loose matter and? What about the law of conservation if so??
« Last Edit: 17/04/2009 21:26:14 by yor_on »
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Offline Vern

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« Reply #25 on: 17/04/2009 21:55:23 »
Quote from: yor_on
Looking on it like that it makes sense in believing that Black holes is formed at the beginning of spacetime, as we can't really have 'super vacuum cleaners' eating up all 'matter/mass'. that as if matter never reaches that 'dimensionless' point 'spacetime' will have a certain density?? Otherwise it seems to me like the universe would loose matter and? What about the law of conservation if so??

I suspect that we will eventually find some principle of nature that prevents matter being condensed down to a singularity. My feeling is that singularities are not normal in nature. One thing I can think of is the composition of matter. Just exactly what is mass. We like to think of it as hv/cc plus momentum. It seems to me that a black hole would take away the v, leaving only constants. That should make it difficult to conserve massivness, which a black hole is supposed to do.

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Offline JP

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« Reply #26 on: 17/04/2009 22:14:17 »
There's a point here where I can't connect the two ways of thinking of a black hole.

On the one hand, you can calculate the maximal pressure exerted by the Pauli exclusion principle and figure out how much gravitational pressure you need to overcome that.  In this argument, the black hole limit is set by the point at which gravity overcomes all other quantum pressures.

On the other hand, you can just look at the mass of a Schwarzschild-object and calculate its event horizon.  If the entire object falls within its event horizon, then you have a black hole, since nothing inside this event horizon can communicate with anything outside of it, and anything inside will inevitably move towards the singularity.  (For rotating black holes, you have a different kind of event horizon, and I have no idea if you can make the same arguments.) In this argument, you simply need to know the density of the object and general relativity instantly tells you where the singularity is.

One of these arguments compares gravity to quantum effects to give you a black hole limit, and one just requires you to know gravity... so how do they relate to each other?

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Offline yor_on

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« Reply #27 on: 17/04/2009 22:42:41 »
Yep Vern, maybe there are such a principle. The thing about the Schwarzschild metric seems to be that there is no un-spinning Black holes found? Am I right there??

If you add the framedragging caused by spinning very massive something something :) then the space around such a object must be very strange. And it seems also a good proof of that nothing 'existing inside' spacetime ever reaching 'c' (ah, except light, that is). But its also very strange in that we can't expect it to be 'fermions' any longer inside that event horizon, if we assume (dangerous word that one) that it will have some sort of 'dimensionless point' to it. So what we have if so is something super massive, not consisting of anything known, rotating near 'c' and working both as 'gravity', and also as 'relative mass' due to its spinning. Seen as such it's Lightarrows example of light having 'mass' come through :)
« Last Edit: 17/04/2009 22:47:40 by yor_on »
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« Reply #28 on: 17/04/2009 23:11:16 »
I remember reading scientific articles which suggested that when a Black Hole forms in our frame of space and time, a White Hole is produced elsewhere. I'm sure this is just speculation without much supporting evidence. Nevertheless, it is an interesting scenario. This has raised another question that you fellows may be able to shed some light upon.

If a White Hole is created along with Black Hole formation, is it not also possible that this presumed White Hole is not just elsewhere in our universe, it may have been displaced into a different time frame. Even more curious is the possibility that this White Hole may have traversed into a different dimension. This may explain the discrepencies with regard to the conversation of mass.

What do you fellows think??

.................Ethos

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Offline yor_on

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« Reply #29 on: 17/04/2009 23:19:20 »
You know Ethos, it would be so much simpler if what we call Black holes instead would be 'White holes'. Which takes me to my question of today/night :)
How can we differ between them, observing those objects in Space? Is there anyone who can explain that in simple terms to me? That as I understand both of them, from our frame of reference, to attract mass?
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Ethos

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From neutron star to Black Hole...........?
« Reply #30 on: 17/04/2009 23:30:12 »
That as I understand both of them, from our frame of reference, to attract mass?
I'm not familiar with that point of view. I was under the impression that a few scientists had proposed that quasars were likely candidates for White Holes. As the amount of energy being released from these objects was well above what anyone had expected. That being the case, some had theorized that these quasars were expelling matter and energy to such a high degree that the only compatable explanation would be that they were exit points for the masses found in Black Holes.

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Offline Vern

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From neutron star to Black Hole...........?
« Reply #31 on: 17/04/2009 23:31:33 »
It doesn't work for me that a white hole, whatever that is, would be created alongside a black hole. I haven't yet mastered the concept of a black hole. I can't get past the concept that we have a singularity that can somehow conserve massiveness. To me it just don't compute. [:)]

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Offline Vern

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From neutron star to Black Hole...........?
« Reply #32 on: 17/04/2009 23:36:10 »
Quote from: Ethos
That being the case, some had theorized that these quasars were expelling matter and energy to such a high degree that the only compatable explanation would be that they were exit points for the masses found in Black Holes.
I like this idea, but I would simplify it. Maybe our supposed black holes radiate all the mass they accumulate in a ray parallel to the plane of their accretion disks. When we happen to be in the line of fire, so to speak, we see a massive amount of radiation. It might look a lot like a quasar.

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Ethos

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From neutron star to Black Hole...........?
« Reply #33 on: 18/04/2009 00:21:04 »
I like this idea, but I would simplify it. Maybe our supposed black holes radiate all the mass they accumulate in a ray parallel to the plane of their accretion disks. When we happen to be in the line of fire, so to speak, we see a massive amount of radiation. It might look a lot like a quasar.
Interesting...........Let's take this idea and run with it for a while.

Assuming that the accretion disk is responsible for quasars, and taking note of the time sequencing of these events, one has to ask the following question:

We have in the center of our galaxy a presumed Black Hole. In fact, it has become a rather common and reasonable assumption that just about every galaxy of any normal size has one at it's center. And these galaxies in question are believed to be very old, much older than the quasars. The bulk of quasar activity is believed to be from very early formations shortly after the Big Bang. That being said; If we are seeing two representations of the same object, as Vern has suggested, and understanding the vast time differential between the two, we may be observing a time loop of sorts. Could this be evidence for a steadystate universe? Mind you, I presently hold to the standard model myself but this question does make one think, doesn't it?

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Offline yor_on

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From neutron star to Black Hole...........?
« Reply #34 on: 18/04/2009 00:23:40 »
That as I understand both of them, from our frame of reference, to attract mass?
I'm not familiar with that point of view. I was under the impression that a few scientists had proposed that quasars were likely candidates for White Holes. As the amount of energy being released from these objects was well above what anyone had expected. That being the case, some had theorized that these quasars were expelling matter and energy to such a high degree that the only compatable explanation would be that they were exit points for the masses found in Black Holes.

"In astrophysics, a white hole is the theoretical time reversal of a black hole. While a black hole acts as a vacuum, drawing in any matter that crosses the event horizon, a white hole acts as a source that ejects matter from its event horizon. The sign of the acceleration is invariant under time reversal, so both black and white holes attract matter. The only potential difference between them is in the behavior at the horizon."
http://en.wikipedia.org/wiki/White_holes

"Yes, the matter that the white hole spits out is attracted to the hole. So is Hawking radiation, but it escapes to infinity anyway. To understand where the distinction between black and white holes comes from, consider the graph of r(t) = \sqrt{k + (ct)^2} for different values of k. (c is the speed of light and r is a kind of radius.) For k > 0 this is a nice smooth curve (half of a hyperbola). This is the surface of an ordinary gravitating spherical object in Kruskal-like coordinates. For k = 0 it reduces to r = | ct | , which has a sharp 90-degree turnaround in the middle where r(t) goes from "inward at the speed of light" to "outward at the speed of light." The inward half is the white hole horizon and the outward half is the black hole horizon. All of the usual "black hole" solutions to general relativity (like Schwarzschild and Kerr) are really gray holes with both black and white hole horizons in them. More realistic classical models have only the black hole horizon. But the whole business seems rather artificial -- maybe the correct description is more like the k > 0 case, where the white-black distinction is inherently absent. Hawking radiation makes this more plausible -- maybe it is the time reversal of absorption in quantum gravity. -- BenRG 23:55, 1 December 2007 (UTC)

        Black holes attract matter, which passes through a wormhole and exits via a white hole. However, Einstein's gravitational field equations only predict this if the mass of the black hole is 0, which is obviously impossible since black holes form from star collapse. Also, if anything with any mass enters a massless black hole, its associated wormhole and white hole will immediately cease to exist. In other words, white holes don't exist. --Bowlhover 16:12, 2 December 2007 (UTC)

I don't see the article on white holes, saying they don't exist. Before we can say something exists or not, it has to be accepted in the scientific community. 64.236.121.129 15:33, 4 December 2007 (UTC)"

------

It wouldn't be simpler would it :)
Then we should have an increased density I presume?
Or?

------Quotes--

What is a white hole? (Karen Masters, 2002)
The short answer is that a white hole is something which probably cannot exist in the real universe. A white hole will turn up in your mathematics if you explore the space-time around a black hole without including the star which made the black hole (ie. there is absolutely no matter in the solution). Once you add any matter to the space-time, the part which included a white hole disappears.

What would a white hole look like if it did exist?
The people/person who came up with the term 'white hole' was actually being quite literal. A white hole is pretty much like an 'anti-black hole'. A black hole is a place where matter can be lost from the universe. A white hole is a place where (if it could exist with any matter in it - which it can't) matter would pop out into the universe. This has many similarities to the Big Bang singularity.

Something Interesting to think about
It has been suggested by Stephen Hawking that once quantum effects are accounted for, the distinction between black holes and white holes is not as clear as it may seem. This is because of Hawking radiation which shows that black holes can lose matter. A black hole in thermal equilibrium with surrounding radiation might have to be time symmetric in which case it would be the same as a white hole. This idea is controversial, but if true it would mean that the universe could be both a white hole and a black hole at the same time. Perhaps the truth is even stranger. In other words, who knows?

-------End---

« Last Edit: 18/04/2009 01:21:36 by yor_on »
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Offline LeeE

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From neutron star to Black Hole...........?
« Reply #35 on: 18/04/2009 00:47:09 »
There's a point here where I can't connect the two ways of thinking of a black hole.

On the one hand, you can calculate the maximal pressure exerted by the Pauli exclusion principle and figure out how much gravitational pressure you need to overcome that.  In this argument, the black hole limit is set by the point at which gravity overcomes all other quantum pressures.

On the other hand, you can just look at the mass of a Schwarzschild-object and calculate its event horizon.  If the entire object falls within its event horizon, then you have a black hole, since nothing inside this event horizon can communicate with anything outside of it, and anything inside will inevitably move towards the singularity.  (For rotating black holes, you have a different kind of event horizon, and I have no idea if you can make the same arguments.) In this argument, you simply need to know the density of the object and general relativity instantly tells you where the singularity is.

One of these arguments compares gravity to quantum effects to give you a black hole limit, and one just requires you to know gravity... so how do they relate to each other?

I see working with the Pauli exclusion principle and quantum pressures as giving you an explanation of why a black hole forms, whereas working with the Schwarzchild solution just tells you the consequences of that event occurring, but doesn't attempt to explain why; it just says that in these conditions, this will occur.

The Schwarzchild solution really just says that something must happen as a consequence of 'c' being exceeded somewhere, whereas the QM solution goes a bit deeper into it.  I think this example really typifies why QM is the dominant theory - it attempts to go further/deeper than Relativity.
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Offline Vern

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From neutron star to Black Hole...........?
« Reply #36 on: 18/04/2009 01:30:44 »
Quote from: Ethos
Could this be evidence for a steadystate universe? Mind you, I presently hold to the standard model myself but this question does make one think, doesn't it?
There seems to be a growing number of physicists willing to entertain the notion of a steady state universe. It will be interesting to see how it finally comes down. But I don't expect to live long enough to see the resolution. [:)] In the meantime, we can only play with the toys we have. Those are the Big Bang theory and Black Holes.

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Offline yor_on

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From neutron star to Black Hole...........?
« Reply #37 on: 18/04/2009 02:45:33 »
They are mighty big toys Vern :)
And even better, they take no room ::))
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Offline JP

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From neutron star to Black Hole...........?
« Reply #38 on: 18/04/2009 05:16:25 »
I see working with the Pauli exclusion principle and quantum pressures as giving you an explanation of why a black hole forms, whereas working with the Schwarzchild solution just tells you the consequences of that event occurring, but doesn't attempt to explain why; it just says that in these conditions, this will occur.

The Schwarzchild solution really just says that something must happen as a consequence of 'c' being exceeded somewhere, whereas the QM solution goes a bit deeper into it.  I think this example really typifies why QM is the dominant theory - it attempts to go further/deeper than Relativity.

Well I guess part of the question is this: is the concept of an object falling within its own event horizon equivalent with gravitational collapse?  I'm guessing the answer is yes, due to the way things behave inside the event horizon (they have to collapse inward).  I'm also guessing, though I've never seen a proof, that long before you add enough mass so that an object falls within its own event horizon, its already gone past the point of gravitational collapse. 

After reading this question, I went back to some notes from when I took a course on general relativity.  We derived the Schwarzschild solution and then stated that because of how things behave on each side of the event horizon, this has to be a "black hole."  Then we justified the existance of a black hole by looking at the masses that would be required for a black hole to form via gravitational pressure considerations, but we never linked the two.

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Offline om

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« Reply #39 on: 18/04/2009 05:58:22 »
Quote
I suspect that we will eventually find some principle of nature that prevents matter being condensed down to a singularity. My feeling is that singularities are not normal in nature. One thing I can think of is the composition of matter. Just exactly what is mass. We like to think of it as hv/cc plus momentum. It seems to me that a black hole would take away the v, leaving only constants. That should make it difficult to conserve massivness, which a black hole is supposed to do.

Detailed studies of the properties of ordinary nuclei have already revealed strongly repulsive interactions between neutrons that prevent the formation of black holes.

[See: "Neutron repulsion confirmed as energy source", Journal of Fusion Energy 20, 197-201 (2003)].

http://www.omatumr.com/abstracts2003/jfe-neutronrep.pdf

Furthermore, these studies show that neutron-emission from a neutron star "may release up to 1.1%-2.4% of the nuclear rest mass as energy".  By comparison, only about 0.8% of the rest mass is converted to energy in Hydrogen fusion and only about 0.1% of the nuclear rest mass is converted to energy in fission.

Therefore massive, energetic celestial objects are not black holes at all, but neutron stars that are highly energized by repulsive interactions between neutrons.

With kind regards,
Oliver K. Manuel
http://www.omatumr.com/

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Offline yor_on

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From neutron star to Black Hole...........?
« Reply #40 on: 18/04/2009 10:14:45 »
If one presume that a white hole is very alike a Black one, then it too will have a 'point' of gravity inside it. That 'point' can't be fermions any longer. If it is so then what it might be trying to 'spew' out would be 'pure mass' whatever that will be. I'm guessing on something similar to bosons, but maybe not interacting with our spacetime as such. That is as if there exist something being of 'primary' constituents, that creates a Big Bang. If so then there is no problem with it from our point of view as it have been 'transitioned' into a state without interaction with us.

If that is possible then those 'white holes' could be what once created mass and space although they then must have been at another state of their formation. That would explain why we seem to find them in every Galaxy. There must be a reason to those 'super massive' gravity wells inside our galaxies. And yes, it's only a idea :)
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Offline Vern

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From neutron star to Black Hole...........?
« Reply #41 on: 18/04/2009 16:00:50 »
If one presume that a white hole is very alike a Black one, then it too will have a 'point' of gravity inside it. That 'point' can't be fermions any longer. If it is so then what it might be trying to 'spew' out would be 'pure mass' whatever that will be. I'm guessing on something similar to bosons, but maybe not interacting with our spacetime as such. That is as if there exist something being of 'primary' constituents, that creates a Big Bang. If so then there is no problem with it from our point of view as it have been 'transitioned' into a state without interaction with us.

If that is possible then those 'white holes' could be what once created mass and space although they then must have been at another state of their formation. That would explain why we seem to find them in every Galaxy. There must be a reason to those 'super massive' gravity wells inside our galaxies. And yes, it's only a idea :)

I tend to speculate in the opposite direction. Instead of imagining new and more exotic realities, I imagine less and more simple realities. This finally took me to the realization that we can not prove by any experiment we can devise even with unlimited resources, that there exists any physical reality other than the electromagnetic field.

So we cannot disprove a notion that was widely held at the turn of the 20th century. That notion is:
The final irreducible constituent of all physical reality is the electromagnetic field.
« Last Edit: 18/04/2009 16:04:46 by Vern »

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Offline yor_on

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From neutron star to Black Hole...........?
« Reply #42 on: 18/04/2009 23:24:16 »
Vern, why so prosaic?
Life is filled with mystery's.

Like, where my glasses have gone?
:)
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Offline LeeE

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From neutron star to Black Hole...........?
« Reply #43 on: 18/04/2009 23:41:44 »
Well I guess part of the question is this: is the concept of an object falling within its own event horizon equivalent with gravitational collapse?

Hmm... good question.  I'll play devil's advocate and say no, because gravity may not be the only means by which an object may be compressed so that it lies entirely within its Schwarzchild radius; pressure could be applied externally to cause the compression (I'm thinking of things like explosive compression, where an explosive shell surrounding an object explodes inwards as well as outwards, or some other ideas I've heard about, using lasers to compress minute amounts of matter).  In these cases, gravity only becomes a 'special' factor after the BH has formed.

Just playing Devil's advocate though - I don't really have an opinion/answer on this.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline yor_on

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From neutron star to Black Hole...........?
« Reply #44 on: 19/04/2009 02:12:38 »
So is there any 'constant' number for this?
Compression ratio relative its size/density. As the idea seems to go out on that no matter how small or big or dense it (that particle/matter) is, there will always be a 'magic' moment where its compression then will force it into a 'Black hole'??
« Last Edit: 19/04/2009 10:22:12 by yor_on »
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Offline Vern

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« Reply #45 on: 19/04/2009 17:57:59 »
I recently read of a study that concluded that a black hole could not form out of an accretion disk because of the spinning action. If so that would only leave the exploding star scenario. I can't find the link right now; I think it was from a link posted by yor_on a few days ago.

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Offline yor_on

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From neutron star to Black Hole...........?
« Reply #46 on: 19/04/2009 18:22:59 »
Here is another link, only a computer simulation though.
http://www.sciencenews.org/view/generic/id/37200/title/No_naked_black_holes
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Offline Vern

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« Reply #47 on: 19/04/2009 18:38:21 »
Quote from: yor_on's link
Mathematically, “naked” singularities, or those without event horizons, can exist, but physicists wouldn’t know what to make of them. All known mechanisms for the formation of singularities also create an event horizon, and Penrose conjectured that there must be some physical principle — a “cosmic censor” — that forbids singularity nakedness, explains coauthor Emanuele Berti of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “We hope it’s true,” he says of the cosmic censorship hypothesis, “because it basically hides the failures of general relativity behind the event horizon.”
Hey; I think I found the cosmic censor.  [;D]
Quote from: my thread in the new theories forum
An example of pure speculation leading to something that may have more wide ranging implications is the contemplation of how gravity might affect gravity in the formation of a black hole. Since time is part of the equation for gravitational acceleration and time is dilated in strong gravitational fields, gravitational acceleration must also be reduced in strong gravitational fields.

Then this fact might be useful in understanding the anomaly we see in some galaxies where the outer stars move too fast. The effect described above would cause a gravitational depression toward the centre of massive galaxies. There would be a halo effect where more gravity than expected would concentrate in the outer reaches of the galaxy.
« Last Edit: 20/04/2009 00:41:03 by Vern »

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Offline Vern

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« Reply #48 on: 20/04/2009 16:59:24 »
Quote
Since time is part of the equation for gravitational acceleration and time is dilated in strong gravitational fields, gravitational acceleration must also be reduced in strong gravitational fields.
Okay; somebody modify the equation for gravitational acceleration to include this and dust off a spot on your mantel for the Nobel. [:)]

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Offline litespeed

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« Reply #49 on: 28/04/2009 06:07:34 »
I've been asking whether neutron stars can become black holes in other forums, but this one is the best so far. However, I do not see where Plank Units have been discussed. Since I do not believe in singularities, it seems to me a black hole would include, at its center, an empty volume with the diameter of one plank unit.

In one of the other forums I asked some questions on relativity. 1) as matter accelerates into a BH does it gain mass? 2) As it approaches the speed of light does time come to a virtual halt?

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