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Dremmer
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If proton decay does not occur, are neutron stars immortal? I was hearing that that was the case.
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RocketSci5KN said:Well, I would think so. Clearly the neutrons are as stable as if they were in a nucleus, so the 'free neutron' half life (614 sec) doesn't apply. Some could decay into a proton and electron, but a large part of the star started out this way, and clearly neutrons are energetically preferred. I suppose it would just slowly cool off by radiating away photons until it matched the cosmic background temp...
Here's a question: Is the density of a neutron star higher at it's core than at the surface? Is there a theoretical limit to this density?
vanesch said:I don't know if there is something like "evaporation" of a neutron star, like there is evaporation of a black hole (assuming Hawking radiation to be true).
twofish-quant said:I don't think that neutron stars are immortal, because if there is proton decay then this will change neutron stars, but their lifetimes are much larger than the age of the universe.
twofish-quant said:Question: Does anything in Hawking's calculation require that the object producing radiation be a black hole? Does the Earth put out Hawking radiation?
bcrowell said:You only get Hawking radiation if there's an event horizon. An event horizon is a defining characteristic of a black hole.
twofish-quant said:For that matter a lot of the thermodynamic results that come from black hole seem to hold if you apply them to *any* boundary.
bcrowell said:I have never heard anyone suggest that, e.g., the Earth would evaporate on long time scales.
I think that's just plain wrong
if you think it's correct, please provide some evidence.
If you can get Hawking radiation observable from infinity in an asymptotically flat spacetime, from an object that has no event horizon according to an observer at asymptotic infinity, then I suppose proton decay would follow trivially from the existence of Hawking radiation??
twofish-quant said:Or electron decay. Suppose we establish that any massive object will produce Hawking radiation. What does that mean for an electron?
Chronos said:Question - assuming Earth suddenly collapsed to form a black hole [reasons irrelevant], what would be its event horizon radius?
Penrose would love it, wouldn't he? ;-)twofish-quant said:Suppose we establish that any massive object will produce Hawking radiation.
twofish-quant said:I need to go through Hawking's papers, but off the top of my head, I don't quite see quite why this is true. The event horizon is a global boundary, and when you cross an event horizon, there is nothing to tell you that you've crossed the event horizon.
The gravitational field of the Earth should be producing pairs of matter/anti-matter and if the anti-matter gets annihilated then you should see some radiation leakage through a Hawking like process.
For that matter a lot of the thermodynamic results that come from black hole seem to hold if you apply them to *any* boundary.
Chimps said:It's the event horizon which creates the effect.
You won't see it on anything without an event horizon because without it, the pairs will annihilate.
The idea is that the curvature of space-time is what causes the virtual particles not to annihilate. If the tidal forces are sufficiently great, the virtual particles will be pulled apart and not be able to annihilate. The energy to create these new particles would come from the space-time curvature, and thus from whatever mass is producing it. It does not seem like an event horizon would be needed. The only limits on the radiation would be that the smaller the curvature the lower the energy (including rest mass) of the pairs produced.TheTechNoir said:It doesn't make sense to me that virtual particle annihilation located on or around something would somehow make mass decrease and if that were the case the smaller an object was, such as my house the more rapidly it would evaporate.
Dremmer said:I remember once reading a while ago that neutron stars could in the distant future quantum tunnel into black holes? Is that actually the case, or just a myth?
Dremmer said:I remember once reading a while ago that neutron stars could in the distant future quantum tunnel into black holes? Is that actually the case, or just a myth?
IsometricPion said:The idea is that the curvature of space-time is what causes the virtual particles not to annihilate. If the tidal forces are sufficiently great, the virtual particles will be pulled apart and not be able to annihilate. The energy to create these new particles would come from the space-time curvature, and thus from whatever mass is producing it. It does not seem like an event horizon would be needed. The only limits on the radiation would be that the smaller the curvature the lower the energy (including rest mass) of the pairs produced.
The wikipedia pages on Hawking Radiation and the Unruh Effect together imply that an observer at infinity will observe a non-zero temperature for any object that produces acceleration. Since all gravitating objects cause the acceleration of all other objects, all gravitating objects should produce Hawking Radiation. As the Unruh article says, there is an event horizon produced by acceleration in Special Relativity called the Rindler horizon, this is a general result of acceleration, gravity is not required. (So, in a certain sense, we were both correct, an effective horizon is (probably) required, but a black hole is not.)Chimps said:It is the unique nature of the event horizon which prevents otherwise certain annihilation.
A neutron star is a type of celestial object that forms when a massive star runs out of nuclear fuel and collapses under its own gravity. The core of the star is compressed to the point where protons and electrons combine to form neutrons, hence the name "neutron star".
Neutron stars are not technically immortal, as they will eventually cool down and become black dwarfs. However, this process can take trillions of years, which is significantly longer than the current age of the universe. Therefore, for all practical purposes, neutron stars can be considered immortal.
Neutron stars are incredibly hot, with surface temperatures reaching up to 1 million degrees Celsius. However, their interiors can reach temperatures of over 100 million degrees due to the intense pressure and energy released during the collapse of the star.
Yes, neutron stars emit light in the form of X-rays, gamma rays, and radio waves. This is due to the extremely high temperatures and strong magnetic fields on the surface of the star, which cause particles to emit radiation.
It is highly unlikely that anything could survive on the surface of a neutron star. The intense gravity and extreme temperatures would make it nearly impossible for any known form of life to exist. However, some scientists believe that there could be habitable zones within the strong magnetic fields of neutron stars, but this is still just a theory.