do massive objects have a "unstable" region near the degeneracy overcome point?

[sarepairman2]

As we know, it seems that most massive stellar objects have some kind of mass threshold prior to changing phase (i.e. white dwarf > neutron star > quark star?> black hole)

Assuming heavy shielding (light years of lead)

if a particle beam cannon is made that is capable of shooting single particles (lets say light leptons ) at the star, will the star collapse at a single point, or will it enter a unstable region where its own internal stresses/vibrations/thermal waves/etc will cause a collapse, i.e. that the transition point from quark star to black hole follows some kind of probability distribution function related to mass?

i.e. does a star behave like a noisy comparator that has its input voltage (mass) shifted, so the exact transition is indeterminable.

i think the answer is yes

[IanB]

Perhaps you have been watching this video? If you have, you should watch it again. If you listen carefully, it tells you that the collapse of a star is caused by the force of gravity--it doesn't happen just by chance. In order to collapse to a denser form, the star needs to be more massive, and therefore to have more gravity. A star isn't going to collapse just because you prod it a little.

[sarepairman2]

its not caused by gravity, its caused by a force overcoming the degeneracy pressure, it is a pressure related phenomena to my understanding. you can create a black hole using light, high energy collisions too probobly

if you have a pool of water with waves you will get reflections and peaks, aka points of additional pressure

[Berni]

I am just guessing here but maybe its similar to radioactive decay. There a atom has a certain chance of decaying. You have no idea when exactly it will decay, there is just a certain probability it will happen within a certain time frame.

I would imagine this would work in a similar way, so adding mass to something that's just on the edge of becoming a black hole would just slightly increase the probability of it happening.

By the way this "triggerable black hole" does sound like a sci-fi futuristic weapon of mass destruction. Is it used yet in any sci-fi novels?

[rs20]

its not caused by gravity, its caused by a force...

Why sir, it's not a peach, for it's a fruit!

The pressure is caused by gravity. Degeneracy pressure is pushing the particle apart yes -- but they'd just fly apart if gravity wasn't pushing them back together.

Just think about a table leg with something heavy on it. There's a lot of electrostatic repulsion going on in the table legs that pushes up on the load on the table. But the only reason there's a load to push up on is the gravitational force pulling down on the heavy things.

Put another away, forces are balanced in a static system.

[rs20]

As for the original question, I don't think a prod is going to trigger a collapse. As far as I understand, a star collapse is a runaway process -- degeneracy pressure is overcome in the centre of the star, density increases, star shrinks, and inverse square law dictates that whatever's now near the centre of the star is now beyond degeneracy pressure. Clearly, the inevitable outcome of this is a complete collapse.

If the the pressure at the centre is at 99.9% of degeneracy pressure, and you prod it, you might succeed at getting a small pocket to collapse -- but the decrease in radius is only going to bring the steady-state pressure in the centre to 99.90000001%, so the runaway won't be initiated.

So for an electrical analogy, it's like a MOSFET runaway situation -- you need a disturbance of a similar magnitude to the energy involved to influence the outcome.

[orolo]

There is a problem describing transitions of big material systems like starts: a star is studied from a statistical point of view, using an equation of state which depends on its gravitational potential (its radius, essentially) and its chemical potential (its mass, essentially). Both mass and radius guarantee wheter a star is stable as a white dwarf or a neutron star, depending on the equation of state. The statistical description is time independent, so transitions are hard to describe.

Assume that you have a stable white dwarf, and you slowly seed it with particles. You will be increasing its chemical potential (mass) up to a point where there is no possible stability as a white dwarf, from a statistical point of view. This huge material system will have to transition to a stable state, respecting the laws of physics, second law of thermodynamics included. The most probable outcome is: unstable white dwarf -> hot neutron star + hot nebula. The reason being that the white dwarf will tend to contract into a neutron star (which is stable at a higher mass), but in order to contract (reducing its entropy) it must get very hot to compensate. If the heating of the neutron star is not enough to compensate for the contraction, or the mass to high (neutron starts have a mass limit) a sizable amount of gas should expand away, greatly increasing the entropy of the final states. A supernova, in brief. The final states, neutron star + nebula, are each stable.

The problem of the statistical description is that it does not give very much information about how the transition happens. However, any statistical system has local fluctuations in energy. Near to the core of the white dwarf, the energy barrier for the transition from degenerate matter into neutron matter is lowest. At some point, a fluctuation near the core will overcome the barrier and cause a local 'nucleation' into neutron matter, with a huge emission of heat. That will cause a steady fluctuation, so to speak, resulting into a runaway condensation into neutron matter. The huge emission of energy should cause the outer parts of the star, which are under less gravitational potential, to be expelled away in the form of a nebula. This process should be irreversible, that is, there is no oscillation between white dwarf and neutron star, since entropy is continually increasing.

In a way, this process of nucleation can be seen in the case of a seed crystal thrown into a saturated solution:

https://youtu.be/MBI39y941GU

[CatalinaWOW]

The answer is in between.  Yes, a star near its collapse point will behave statistically.  That is, the closer it is to the collapse point the higher the probability that the process will cascade.  Equally, the further beyond the nominal collapse point, the lower the probability that the cascade will not have started yet.

Your single particle cannon will be a useless tool to investigate this.  Single particles will be negligible to the probabilities involved.  Also, while I haven't done the math to verify this, even if you were dropping large mass increments onto this star, the transit time for the change in state is likely to be large relative to the timescale of the probabilities of the cascade.  The cascade events initiate in the center of the star, and density changes propagate at the speed of sound, taking days to go from the surface to the center.  While the gravitational change arrives far more quickly, it would result in density changes much smaller than the acoustic fluctuations going on all of the time.

[T3sl4co1l]

Degeneracy pressure has to do with the energy a particle has, and the size it can be constrained to.

Pressure is highest in the center, so that will be the point of collapse (into a smaller degeneracy mode, such as white dwarf --> neutron, or neutron --> [possible exotic forms] --> final black hole).

There could be local disturbances (star quakes; collisions; perhaps nuclear reactions triggered by higher density?) which create pressure waves that trigger this behavior, but it's still likely to happen in the center (or at least on the rotational axis, where there's no centrifugal force to reduce pressure).

Anyway, the physical explanation is that, as a given particle is confined to a smaller and smaller space, its energy (and therefore temperature) doesn't track proportionally, due to relativity.  So as size approaches zero, energy remains finite.  The curve of size(white dwarf) vs. mass generally goes down, but it goes down hyperbolically as you approach the Chandrasekhar limit, at which point the assumed physics (degenerate electrons) break down and, at some point down that curve, other interesting things happen (i.e., reverse neutron decay).

Obviously, as the degeneracy breakdown process is going on, volume is decreasing and density is increasing, which increases the probability of conversion.  This would begin as a small background rate, for example in high density dwarfs, there would be a gradual enrichening of neutrons.  Which might be confirmed through x-ray spectra emitted or reflected from the star's surface corresponding to neutron-rich elements; but, it would be a slow process, so it wouldn't really be something that can be observed over scientifically useful time scales (Gyr?).

If mass is being added to drive the star closer to the threshold (i.e., it's still accreting), neutron production probably wouldn't be visible on top of the infalling matter (and probable fusion reactions, including novae..).  So in this case, it would just gradually shrink, until one day, poof, in a big explosion, it becomes a neutron star (or whatever).

The reverse-neutron decay process is endothermic (indeed, the conversion of an entire star's worth of electrons into neutrinos is a large fraction of the total energy output of this type of supernova!), but there will be a lot of fusion going on as the increasing density pulls hydrogen (including newish deuterium and tritium), helium and more together.

Note that a black hole is not degenerate matter; in a pragmatic sense (i.e., in terms of anything that can be observed externally), it isn't made of matter at all, it's just a very massive hole in space-time.  A property of space-time curvature, corresponding to a sufficiently dense mass charge, but with no identity such as particle resonances or stuff like that, only the most basic bulk properties of electric charge, spin (mechanical charge; a consequence of the symmetries of 3D space) and mass (space-time charge).

The mass within may still be due to baryonic matter-as-we-know-it (and energy), but it falls towards a singularity, and can never communicate with the outside-world-as-we-know-it, because all causal lines (geodesics) spiral inward.  Clearly, such matter is getting very close together, implying special quantum physics (ever smaller distance scale, ever larger energy scale), but we don't have any present theories on what happens under such conditions.

Tim

[sarepairman2]

dark energy star is the most curious explaination...

[T3sl4co1l]

dark energy star is the most curious explaination...

Dark energy and mass have very little if any relevance on stellar scale objects.  Up to planetary size systems or so.

We're still figuring out how significant the effects are on galactic-scale objects, but still, that's a half dozen orders of magnitude between.

Tim

[sarepairman2]

https://en.wikipedia.org/wiki/Dark-energy_star

the idea of proton decay near the event horizon makes sense to me, i see it as field lines getting really really intense so that particles are ripped apart as much as possible, so each of the sub-particles can follow its little field line train track into the event horizon, at least on smaller black holes..

idk how this dark energy spagetification is explained on large event horizons though

[T3sl4co1l]

Doesn't make much sense:

To an outside observer, the event horizon is just that: the point beyond which no events (or information or light) can pass, in finite proper time.  This makes it special enough to define.

To an infalling observer, it's arbitrary; nothing fundamentally changes, except that, no matter which direction you move in, nor how fast, you can only continue to spiral inward.  Local space is still space you can move around in.  Though, how far depends on the curvature: for an observer the size of a human, say, it would be much kinder to fall into a supermassive black hole (where it might be much like freefalling towards a planet, until you're rather deep within), than a stellar-mass one, or even smaller, where the gravitational shear might spaghettify you well before the event horizon!

Deeper inside, though, there's no doubt that space gets "tighter and tighter", so to speak, which is also a problem for QM.  It doesn't make sense for particle physics to break down at the event horizon, but it might occur at a sufficiently dense field, much as electric field emission occurs not at a specific voltage barrier, but a sufficiently high electric field strength.

As for proper times, I have no idea.  Special relativity and QM work stupendously well together: QED and beyond are the direct consequence of their combination.  Generalizing that to, well, General Relativity has been quite the challenge though.

Tim