I’ve read some of the major articles available on the Web, but they leave out what will eventually happen to them. They seem to slow down and cool down over time, but eventually will they be just cold blobs floating in space?
TY for your answers.
Eventually, EVERYTHING will be just a cold blob floating in space.
At least that’s true if you don’t subscribe to the Big Crunch idea. And even if you do, there comes the point of maximum expansion where an awful lot of the universe (99.999%+?) is just cold blobs floating in space.
Then the contraction begins, ever … so … slowly … at … first.
How about just an individual neutron star?
Here’s a link.
It’s pretty technical.
From what I gather, they just don’t know.
A lot about neutron stars is still a little theoretical, but I thought the ‘cold ball of neutronium’ was pretty much what the theories we had indicated. Just like most other stars not massive enough to become neutron stars become ‘black dwarves’ - cold balls of highly dense matter, though not nearly as dense as neutronium.
The popular notion that neutron stars are just big blobs of neutrons is both inaccurate and highly contentious. The simple model is that a neutron star is made of neutrons in which atomic structure collapses and the protons and (some) electrons have combined in an inverse beta “decay” to make neutrons, which are all held apart by the remaining electrons via electron degenercy pressure (the “pressure” generated by the inability of two electrons to share the same quantum state per the Pauli exclusion principle). This results in a balance between this pressure and the gravitational attraction between neutrons in which gravity (which is not, as currently understood, a quantitized force), so the resulting interactions are not well-understood. However, under normal conditions a “free” neutron–one not “bound” into a nucleus by the residual strong force will shortly (~11m) decay–so something else is going on to maintain stability.
Under these conditions, some theorize that neutron-neutron interaction–which is typically a nonissue in everyday life–creates an environment where free quarks can exist, or that other exotic particles made of atypical (and nominally unstable) composite particles comprised of quarks and leptons. Since this is all in the realm of highly speculative particle physics–particles that can be mathematically modeled but exist, if at all, only for the briefest of timespans and under bizarre conditions–it’s impossible to say exactly what is going on there.
So, what happens to them in the long term? We can guess that they’ll eventually decay, but whether that happens before/after the universe collapses to a singularity/expands to infinity/dies an informational heat death/recycles into something even more bizarrely inexplicable is anybody’s guess.
Stranger
Ignoring issues to do with the fate of the wider universe, there are several different processes that have been considered that may determine what happens to a neutron star on very long timescales. A couple are mentioned in this John Baez article.
In no particular order and deliberately avoiding putting numbers on the timescales:
[ul]Evaporation. As Baez mentions, the contents of it will gradually boil off, in much the same manner that a planet loses its atmosphere: thermal fluctuations on the surface are sufficient to occasionally kick particles away.[/ul]
[ul]Proton decay. Though in this instance it’s better thought of as quark decay. This will turn the quarks making up the star into the likes of electrons and neutrinos. One wouldn’t expect whether the quarks are confined as nucleons or otherwise to make a significant difference to this process, but one’s always prepared to be surprised.[/ul]
[ul]Monopole-catalysed decay. If the neutron star encounters a magnetic monopole then that sinks to the centre of the star and vastly speeds up the previous process. Main issue here is probably how long you have to wait for the monopole to come along rather than how long it then takes to chew up the star.[/ul]
[ul]Black hole formation via quantum tunnelling. In general, anything is in a “lower” state as a black hole than as itself. And the only reason it doesn’t immediately become one is that there’s a huge great stonking energy barrier in the way. But in quantum mechanics the star can tunnel through this barrier. The only issue then is that the probability of this happening in any normal length of time is - mercifully - so small that it takes, to use some technical language, damn near forever for this to become likely. But if it’s otherwise just going to sit there forever, then one does have to consider this process. Once it’s a black hole, then Hawking evaporation kicks in and the hole gradually decays into radiation.[/ul]
Thus, on the longest of timescales, even neutron stars begin to look like transitory objects that evaporate in one way or another.
The biggest difficulty with these sorts of arguments is that it’s always inherently hard to be sure that you aren’t overlooking some other subtle and enormously rare process, either known or unknown. Related to that is that all this is possibly neglecting process that have to do with the surrounding environment. Thus, for example, it may be an extraordinarily rare event for our hypothetical neutron star to randomly collide with another or a black hole. But that’s the sort of rare event that might become commonplace if you’re waiting 10[sup]10[sup]26[/sup][/sup] years anyway.
That article said something that surprises and puzzles me. The author says
But if even gravity redshifts, then in theory a black hole should have no external gravity at all- the singularity should pinch off from our universe and vanish altogether. (Actually, Isaac Asimov speculated in an essay of his that this was what happened to dense enough objects.) Or is this one of those relativity things in which the gravity is a property of the surrounding space, not the black hole itself?
In the very long term, it’s difficult to say, but see Stranger on a Train and bonzer’s posts for some possibilities. But given how hard it is for most folks to grasp the timescales involved for those processes, I’m going to guess that the OP had something a little shorter-term in mind. Specifically, I’m going to guess that he was wondering if cooling down caused anything interesting to happen to a neutron star. The answer to that one is no. Even a brand-new neutron star, fresh from a supernova, can be considered to an excellent approximation to be at zero temperature. By everyday human standards, of course, the temperature is huge, but the effects of the temperature are far smaller than the effects of the quantum processes behind the degeneracy. So as the star cools, it just goes from an excellent approximation to an even more excellent approximation.