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WaxRubiks
2015-Jun-29, 10:23 PM
Incipient black holes are dense objects where an event horizon and a singularity haven't formed:

https://en.wikipedia.org/wiki/Nonsingular_black_hole_models

If a black-hole-like object existed, then things like radiation, neutrinos, and dark matter(if it is matter) should be able to pass through them, shouldn't they?

If a neutrino passed through one, its passage would be heavily time dilated, but it should get through, shouldn't it?

Would one have to get quite close to a black hole to measure things that may have passed through them?

Reality Check
2015-Jun-30, 01:30 AM
If a "incipient" black-hole-like object existed then it would act like any other dense object. Neutrinos would pass through it. They may even pass through it easier than planets and ordinary stars. Think about an electron scattering a photon. It needs to absorb it and then emit another photon. An electron in an outer orbital can absorb the photon, jump to a different orbital and emit a photon. An electron in an inner orbital has no available orbitals to jump to - it cannot scatter the photon. It could be that the degenerate matter that this object will fill all available quantum states so that a neutrino cannot be scattered and will pass straight through.

By definition, nothing passes through a black hole. Anything that enters an event horizon does not come out again. But we already have good observations of things that pass close to black holes, e.g. the stars around the Milky Way supermassive black hole.

John Mendenhall
2015-Jun-30, 03:10 AM
Good question, FM. Many posters here can give knowledgable answers. This should be enjoyable.

WayneFrancis
2015-Jun-30, 09:12 AM
The thing about black holes is many people don't realize how close to the EH you need to get to see extreme time dilation. So even if you had solar mass object that was a centimeter larger then it's time dilation is only like 550x
Even so what does that mean? When it climbs back out it is no longer time dilated. Do you care if a neutrino was formed 10 minutes ago or 2 days ago? If you where trying to use those neutrino's to communicate it would be a pain but otherwise there isn't much that it affects.

Cougar
2015-Jun-30, 11:07 AM
Incipient black holes are dense objects where an event horizon and a singularity haven't formed....

AIUI, standard physics predicts no stable bodies between the mass ranges of neutron stars and black holes.

WaxRubiks
2015-Jun-30, 11:29 AM
AIUI, standard physics predicts no stable bodies between the mass ranges of neutron stars and black holes.

I mean "in theory".

I was just saying if you had a black hole type object handy, what tests could you do on it to see if there was an event horizon there?

Grey
2015-Jun-30, 07:20 PM
I was just saying if you had a black hole type object handy, what tests could you do on it to see if there was an event horizon there?My favorite test is one that was done in 2006 (obviously observing something that was happening anyway on distant black hole candidates, rather than a carefully arranged experiment on one that we had conveniently lying around). A team looked at X-ray data from both suspected black holes and neutron stars. For the neutron stars, gas from the accretion disk would regularly impact on the surface and erupt in periodic thermonuclear bursts, generally every few hours. The observations match models of infalling gas on the surface of a dense object very well. The black hole candidates, however, never exhibit such bursts, which suggests pretty strongly that they don't have a solid surface. If the material is instead pulled through an event horizon never to be seen again, that would match the data very well.

WaxRubiks
2015-Jun-30, 08:07 PM
My favorite test is one that was done in 2006 (obviously observing something that was happening anyway on distant black hole candidates, rather than a carefully arranged experiment on one that we had conveniently lying around). A team looked at X-ray data from both suspected black holes and neutron stars. For the neutron stars, gas from the accretion disk would regularly impact on the surface and erupt in periodic thermonuclear bursts, generally every few hours. The observations match models of infalling gas on the surface of a dense object very well. The black hole candidates, however, never exhibit such bursts, which suggests pretty strongly that they don't have a solid surface. If the material is instead pulled through an event horizon never to be seen again, that would match the data very well.

but, if the black hole was really just a dense object a tiny bit bigger than the Schwarzschild Radius then there would be strong time dilation near the surface delaying any X-rays emitted from the surface?

I don't know what type of incipient black holes have been postulated. Are they postulated to be in a constant state of, time dilated, collapse/freefall...? If so would that mean that the X-Rays would be heavily redshifted? Did they look for longer wavelength signals? Would they have to wait millions of years for them anyway?

Grey
2015-Jun-30, 08:47 PM
but, if the black hole was really just a dense object a tiny bit bigger than the Schwarzschild Radius then there would be strong time dilation near the surface delaying any X-rays emitted from the surface?

I don't know what type of incipient black holes have been postulated. Are they postulated to be in a constant state of, time dilated, collapse/freefall...? If so would that mean that the X-Rays would be heavily redshifted? Did they look for longer wavelength signals? Would they have to wait millions of years for them anyway?Well, of course it wouldn't matter if you had to wait millions of years; you'd just get the radiation from a million years ago instead of the radiation generated from infalling material today. The redshift would certainly be an issue, but then you'd probably notice anomalous bursts of radio waves that you'd have to try to explain.

The link you provided doesn't really give any technical details on how such an object is theorized to behave (and indeed, it sounds like it's uncertain whether it's even a theoretically stable possibility). So we'd need more detail on exactly what someone is proposing to know how it might behave and what observations might confirm or contradict whether a candidate object is such a thing.

WayneFrancis
2015-Jul-01, 04:16 AM
but, if the black hole was really just a dense object a tiny bit bigger than the Schwarzschild Radius then there would be strong time dilation near the surface delaying any X-rays emitted from the surface?

I don't know what type of incipient black holes have been postulated. Are they postulated to be in a constant state of, time dilated, collapse/freefall...? If so would that mean that the X-Rays would be heavily redshifted? Did they look for longer wavelength signals? Would they have to wait millions of years for them anyway?

Again it wouldn't be shifted much.
Let me go back and use another example
Say we had a 5 solar mass object that what just 1 millimeter larger then the EH of the same size black hole.
We know material falling on to a neutron star will emit in the gamarays or 10-12m range
Well the dilation from that point is only ~38,000 times which may seem like a very large amount but that isn't even enough to red shift those photons into the visible spectrum. It would be still in the ultra violet.
Upon more investigation it would be slightly worse because the impact would be that much stronger because of the stronger force of gravity the initial release of gamma rays would be even higher in frequency then from a neutron star.

So we'd get a burst of EM but it would not be shifted into the radio spectrum. For that we'd have to go from an object just 1 millimeter larger then a 5 solar mass black hole to an to an object just .00000000001 milimetres larger and even then I'm ignoring the increased energy release from hitting the surface.
Basically you'd need to be just the wavelength of a gamma ray above a potential EH to have a gamma ray shifted into the radio spectrum.

But you where talking about something passing through that object...in which case it wouldn't be red shifted coming back out and would just appear to delay the signal accordingly. Even then the particle would be going so fast that the delay caused by a few dozen km is not going to matter much at all. Lets go with the 38,000 times dilation. You are talking about the travel time being increased by less then 1 second.

Reality Check
2015-Jul-01, 10:26 PM
but, if the black hole was really just a dense object a tiny bit bigger than the Schwarzschild Radius then there would be strong time dilation near the surface delaying any X-rays emitted from the surface?

The problem is that you have no sources for the properties of any "incipient black holes". All we can assume is that the existing physics are correct and so the gravitational field would be comparable to that of neutron stars. They have no problems in emitting x-ray bursts that look like thermonuclear reactions from in falling matter piling up on the surface.

WaxRubiks
2015-Jul-01, 11:12 PM
The problem is that you have no sources for the properties of any "incipient black holes".

yes, that's true. I thought maybe the one property that it maybe should have is that neutrinos would be able to pass through it.
And the time dilation would maybe be huge but not infinite.

Grey
2015-Jul-02, 12:10 AM
Again it wouldn't be shifted much.
Let me go back and use another example
...Nice job working out a rough example. This is exactly why it's often useful to work out the actual numbers. So from Wayne's numbers, it seems pretty clear that some kind of hypothetical stable object smaller than a neutron star but larger than a black hole would have to be almost exactly (to outrageous precision) the same size as a black hole, or the time dilation and gravitational redshift wouldn't significantly affect our observations. It seems unlikely that any of the objects that we've seen that behave like they have definite event horizons could be "incipient black holes".

John Mendenhall
2015-Jul-02, 06:55 AM
Good question, FM. Many posters here can give knowledgable answers. This should be enjoyable.

It is. Thanks to all. Fascinating.