Black Hole Core Mystery

[EWyatt]

Because we already understand the force sustaining the neutron star core and it does not produce densities sufficient to create an event horizon.

 

Now, if are suggesting that neutron star cores are somehow compressible so that, at a certain mass level, the density of the core is sufficient to create an event horizon then you still need to explain why crossing this threshold does not constitute a transition to a new state........

 

 

 

Baric, thanks for the reply. My VERY simplistic reply to the above is that the hypothetical gigantic neutron star would NOT have to compress any further, in terms of normal physics. For all we know, the size of a black hole's event horizon could very well be just "slightly" larger than the actual neutron star itself -- and as we know, neutron stars are VERY dense and gravity intense. There may be a mathematical resolution that states that a neutron star at ANY size could not have sufficient density to form an event horizon, but I haven't come across that yet. Regardless of the many discussions on this thread so far, I see nothing that would exclude this simple possibility.

Again, I'm looking at this from a very basic viewpoint. At times, the answers may lie there.

[Schrödinger's hat]

Baric, thanks for the reply. My VERY simplistic reply to the above is that the hypothetical gigantic neutron star would NOT have to compress any further, in terms of normal physics. For all we know, the size of a black hole's event horizon could very well be just "slightly" larger than the actual neutron star itself -- and as we know, neutron stars are VERY dense and gravity intense. There may be a mathematical resolution that states that a neutron star at ANY size could not have sufficient density to form an event horizon, but I haven't come across that yet. Regardless of the many discussions on this thread so far, I see nothing that would exclude this simple possibility.

Again, I'm looking at this from a very basic viewpoint. At times, the answers may lie there.

 

Look up the Tolman–Oppenheimer–Volkoff limit. I'm pretty sure the Schwarzschild radius is always inside a neutron star unless it is too big to be supported by degeneracy pressure.

[csmyth3025]

...There may be a mathematical resolution that states that a neutron star at ANY size could not have sufficient density to form an event horizon, but I haven't come across that yet. Regardless of the many discussions on this thread so far, I see nothing that would exclude this simple possibility.

Again, I'm looking at this from a very basic viewpoint. At times, the answers may lie there.

As mentioned by SH, the Tolman–Oppenheimer–Volkoff limit provides the mathematical resolution you're searching for:

 

In a neutron star less massive than the limit, the weight of the star is balanced by short-range repulsive neutron-neutron interactions mediated by the strong force and also by the quantum degeneracy pressure of neutrons, preventing collapse. If its mass is above the limit, the star will collapse to some denser form. It could form a black hole, or change composition and be supported in some other way (for example, by quark degeneracy pressure if it becomes a quark star). Because the properties of hypothetical more exotic forms of degenerate matter are even more poorly known than those of neutron-degenerate matter, most astrophysicists assume, in the absence of evidence to the contrary, that a neutron star above the limit collapses directly into a black hole.

 

(ref. http://en.wikipedia....r-Volkoff_limit )

 

As mentioned in the quoted passage: "...most astrophysicists assume, in the absence of evidence to the contrary, that a neutron star above the limit collapses directly into a black hole..."

 

As far as I know, there isn't any "...evidence to the contrary..." yet.

 

Chris

[csmyth3025]

Look up the Tolman–Oppenheimer–Volkoff limit. I'm pretty sure the Schwarzschild radius is always inside a neutron star unless it is too big to be supported by degeneracy pressure.

On the subject of the Tolman-Oppenheimer-Volkoff limit there is a 1995 paper by I. Bombaci (Astronomy and Astrophysics, v.305, p.871) entitled "The Maximum Mass of a Neutron Star". This paper is in pdf format here:

 

http://articles.adsa...8;filetype=.pdf

 

Unfortunately, this paper is way over my head. If one of our more knowledgeable members can translate this paper into something that us mere mortal humans can understand, it might provide the mathematical resolution that EWyatt has been unable to find:

 

EWyatt, on 16 September 2011 - 04:52 PM, said:

 

...There may be a mathematical resolution that states that a neutron star at ANY size could not have sufficient density to form an event horizon, but I haven't come across that yet. Regardless of the many discussions on this thread so far, I see nothing that would exclude this simple possibility.

Again, I'm looking at this from a very basic viewpoint. At times, the answers may lie there.

 

 

In the meantime, I would refer EWyatt to the Wikipedia article on super-massive black holes and, particularly, the passage regarding mass densities contained within the event horizon:

 

...The average density of a supermassive black hole (defined as the mass of the black hole divided by the volume within its Schwarzschild radius) can be much less than the density of water (the densities are similar for 10⁸ solar mass black holes^[5]). This is because the Schwarzschild radius is directly proportional to mass, while density is inversely proportional to the volume. Since the volume of a spherical object (such as the event horizon of a non-rotating black hole) is directly proportional to the cube of the radius, average density decreases for larger black holes, being inversely proportional to the square of the mass.

(ref. http://en.wikipedia....sive_black_hole )

 

My read on this is that the question isn't whether the density of a neutron star (of any size) is sufficient to form a black hole event horizon. The Wikipedia article indicates that the density of ordinary water is sufficient to do that if enough of it is piled up in one place. The question is how big can a neutron star get and still be a neutron star - which I believe is what the paper by Bombaci addresses.

 

Chris

 

This is a bit off-topic, but an interesting experiment for a highly advanced civilization with plenty of time and money on their hands would be for them to pick some out-of-the-way cosmic location and send cargo ships laden with pig iron - which they would eject upon their arrival and then go back to the galactic foundries to get more.

 

At some point in time (millennia?) this huge molten ball of iron (molten from the kinetic energy of dropping off the pig iron in the course of their fly-by maneuvers) would get so big that it would collapse into a -- ? (white dwarf? or, neutron star?). Would this be a cataclysmic event or could it occur gradually (from the inside -->out)?

 

This would be essentially the same as a core collapse of a star, but without the hydrogen, helium and other lighter elements layered on top of it. Would this collapse release energy?

 

Chris

[EWyatt]

Look up the Tolman–Oppenheimer–Volkoff limit. I'm pretty sure the Schwarzschild radius is always inside a neutron star unless it is too big to be supported by degeneracy pressure.

 

Got it, Schrodinger, and thanks for that. Now let me think........

[Widdekind]

Remember, the pressure at the center of a star is much greater than at the mantle. If the core is compressible

 

Neutronized 'neutronium' matter is, like regular rock, a 'structural material'. Neutronized matter has (1) an elastic regime (e.g., core bounce-and-rebound, during the SNe, out of whose ashes, NS's emerge); (2) a plastic regime (e.g., 'border-line' SN / HN, from 'border-line' super-massive / hyper-massive progenitor stars, ~30 M_sol, which generate 'maximal NS' or 'minimal BH'); and (3) a failure regime (e.g., HNe, where gravity crushes the core, without bounce-back).

 

The elasticity, of regular rock, which 'rolls' and flexes during terrestrial earth-quakes, is already difficult to recognize -- 'neutronium' would, in some sense, be 'ultra rock'. But, according to the Teaching Company lecture series Black Holes Explained, by Prof. Alex Filippenko, there is observational evidence, which can be construed, with some objects -- observed to be more massive, and denser, than typical NS -- not emitting radiation, from any visible surface; and, which emit radically red-shifted light, from the inner edges, of their accretion disks. If so, then there is observational evidence, for objects darker, denser, and more extreme, than even NS. Such "dark holes" might not be "infinitely" dense BH... but, never-the-less, some state of exotic-matter more extreme than 'neutronium'. Again, NS are produced in the SNe, of SM-progenitor stars, <30 M_sol. Er go, yet-more-massive, HM-progenitor stars, >30 M_sol, which generate HNe & GRBs, will leave behind "burning embers" commensurately more extreme still.

 

 

 

 

The truthful answer is that we do not understand physics in such extreme gravitational fields. No one really known what lies in the middle of a black hole. But for sure, most physicists believe that the classical singularity is not physically realised...

 

In baryonic matter, 99% of the mass-energy... is 'glue'. The "bare naked" quarks, combined, account for ~10 MeV, out of ~1 GeV per nucleon. Now, according to the Bag-Model of Quark Confinement, a reasonably-accurate potential, for quarks inside nucleons, is V = k r, where k ~ 1 GeV / fm. In particular, the potential is zero at zero separation -- 'glue' is only 'engaged', when quarks start to stray ('when they tug on their tethers, the Color Force yanks their chains, and reels them in'). So, 'glue' is only 'energized' -- i.e., massive -- when quarks start to stray.

 

Thus, as you compress neutronized 'neutronium' matter, why wouldn't you begin to press those quarks together, towards their r --> 0 regime of 'asymptotic freedom' (V ~ 0)? To wit, inside ultra-compact objects, why wouldn't gravitational compression "take over from", and "bear the burden of", the Color Force -- keeping the quarks confined, without the need for 'glue' ? If so, then, as you compressed an object, to densities > 1 / fm³, the quarks would interact less vigorously; produce less 'glue'; and, mass <99% less (to lowest order, [math]M® \propto R[/math]).

Edited September 22, 2011 by Widdekind

[Widdekind]

In SN, which generate NS, one witnesses "matter fall-back", where some baryons fail to escape the compact core's gravity. At higher & higher progenitor masses, wouldn't one witness increasing gravity, s.t. there would be a regime, of "neutrino fall-back"... and then "photon fall-back" ? Such "failed SN", which would generate BHs, might, then, eject no matter; emit no neutrinos; emit no photons. Could you create stellar-mass BHs, in "cloaked covert-ness", by such a "failed SN" scenario ???

 

 

 

Refs:

 

Kolb. Extreme Environment Astrophysics.

Schilling. Flash!

[Genius13]

i have a quetion that might be stupid

why does the matter formed around a black hole alyways have a dick-like shape and not an sfere , take galaxies for axample ,why arent they sfere-like

[baric]

My read on this is that the question isn't whether the density of a neutron star (of any size) is sufficient to form a black hole event horizon. The Wikipedia article indicates that the density of ordinary water is sufficient to do that if enough of it is piled up in one place. The question is how big can a neutron star get and still be a neutron star - which I believe is what the paper by Bombaci addresses.

 

The problem is still density-related, although maybe in hindsight I should have phrased it better. If neutron stars did not collapse to a higher-density state, then yes it is DEFINITELY possible to create an event horizon with sufficient mass at known neutron-star densities.

 

However, the minimum amount of mass required to reach that threshold is most certainly greater than the amount of mass in the smallest stellar black hole discovered (<4 solar masses).

 

This strongly indicates that a black hole has a greater core density and is structurally different than a neutron star.

 

i have a quetion that might be stupid

why does the matter formed around a black hole alyways have a disk-like shape and not an sfere , take galaxies for axample ,why arent they sfere-like

 

Because as matter rotates around the core, it collapses into a disk to conserve angular momentum.

 

Go to the "Protostar" section of this article (http://en.wikipedia.org/wiki/Nebular_hypothesis) for a good rundown.

Edited October 17, 2011 by baric

[Genius13]

ok so here's my quetion

in the inflation theory gravity workd the other way around and pushed matter away from each other

so why doesnt this happen in a black hole??

[baric]

ok so here's my quetion

in the inflation theory gravity workd the other way around and pushed matter away from each other

so why doesnt this happen in a black hole??

 

The inflation theory says that gravity worked in reverse?

 

Can you provide a citation for that?

[Genius13]

actualy i heard it on discovery and in' the brief history of time'

[questionposter]

So there's an extreme concentration of gravity, which is a black hole, but are there extreme concentrations of other forces like the EM force or weak force? Where's my super-magnetic hole?

[baric]

So there's an extreme concentration of gravity, which is a black hole, but are there extreme concentrations of other forces like the EM force or weak force? Where's my super-magnetic hole?

 

Unlike the others, gravity is long-range force, which allows it to accumulate with mass.

[Genius13]

The inflation theory says that gravity worked in reverse?

 

Can you provide a citation for that?

http://en.wikipedia....ationary_models

look under

Early inflationary models

Edited October 19, 2011 by Genius13

[baric]

http://en.wikipedia....ationary_models

look under

Early inflationary models

 

Do current inflationary models still posit a reverse gravity or was that idea discarded?

[Genius13]

still have it as i know ..

[questionposter]

Unlike the others, gravity is long-range force, which allows it to accumulate with mass.

 

But the EM force get's weaker at the same rate as gravity...by the square of the distance.

[Schrödinger's hat]

But the EM force get's weaker at the same rate as gravity...by the square of the distance.

 

That's true, but charges of one kind tend to attract charges of the other, so on large scales they tend to even out, and gravity dominates.

[pantheory]

The conversational theory of what constitutes a black hole core has resulted in many non-answers, some even dealing with an "infinitesimal singularity" which I find ridiculous. Why not just take a logical step back and conclude that a black hole, and its core, is simply a very large, dense neutron star! That would also keep current laws of physics intact, without all those hypothetical black hole hyperboles. Or has this neutron star thing been rebuffed already? Thanks.

I think the problem with considering a black hole as a neutron star type entity lies with the volume of matter equivalence that must be occupied within a volume too small for a neutron star to exist. Of course a black hole could be another unknown more dense form of matter such as a dense conglomeration of dark matter, or other theoretical field material of some kind.

 

The vacuous single point idea was based upon the mathematics of General Relativity and mathematically related models. A different mathematical model seemingly might propose a physical entity instead.

Edited November 1, 2011 by pantheory

[*puffy* japanisthebest]

The conversational theory of what constitutes a black hole core has resulted in many non-answers, some even dealing with an "infinitesimal singularity" which I find ridiculous. Why not just take a logical step back and conclude that a black hole, and its core, is simply a very large, dense neutron star! That would also keep current laws of physics intact, without all those hypothetical black hole hyperboles. Or has this neutron star thing been rebuffed already? Thanks.

M aybe the core of a black hole depends on if it is spinning, how big it is, and how it formed.

[baric]

M aybe the core of a black hole depends on if it is spinning, how big it is, and how it formed.

 

Keep in mind that all black holes are spinning and doing so at an extremely high rate. There's no other way to conserve angular momentum.

 

It's just all happening within the event horizon.

[superball]

some

Why not just take a logical step back and conclude that a black hole, and its core, is simply a very large, dense neutron star! That would also keep current laws of physics intact, without all those hypothetical black hole hyperboles. Or has this neutron star thing been rebuffed already? Thanks.

 

The assumption would be less, and less likely to occur if there was found to be more galaxy's in the universe than neutron stars.

 

On the other hand if a galaxy was formed from a neutron star, the lack of observable neutron stars compared to the amount of observable galaxy, would suggest the universe is even older then previously measured.

 

The statement, some neutron stars may produce a galaxy is still valid IMHO.

 

NAS

 

movie

 

Cheers, super-ball.

Edited November 22, 2011 by superball