Scientists have observed for the first time evidence of the new exotic phase occurring in the material in the inner shell of the neutron star, also known as a pulsar.
Researchers from the University of Alicante have discovered a new phase in the lives of neutron stars. The scientists observed for the first time evidence of the new exotic phase occurring in the material in the inner shell of the neutron star, also known as a pulsar.
The research was published in the journal Nature Physics and it reveals part of the lives of the mysterious pulsari-radio objects. Pulsars are rapidly rotating neutron stars that emit electromagnetic radiation. Their cycle completion speed is incredibly accurate. One of the unsolved questions in this field is whether there is a pulsar that can rotate for more than 12 seconds per revolution cycle or is it a physical limit. Now the scientists have discovered another layer, apparently there is such a limit and it occurs as a result of a new exotic phase of the material.
Jose A. Pons, the lead author of the study says: "This may be the first observational evidence of the existence of another stage in the nuclear "pasta" that occurs inside neutron stars. The discovery may contribute to future tasks of X-ray observations and defining aspects that describe how the nuclear interaction works, aspects that we currently do not have enough information about."
The nickname "nuclear pasta" is given to the phenomenon because it is very similar in appearance to the Italian food pasta. The phenomenon happens when the combination of the nuclear and electromagnetic forces, at a very high density, causes the nuclei of the atoms (made of protons and neutrons) to arrange themselves in a non-spherical manner.
Daniel Vigano, a doctoral student at the university, says that "the pulsars are born while rotating at a very high speed, more than 100 times per second. However, their strong magnetic field slows them down during their lifetime, which increases the rotation cycle time. At the same time, the inner mantle erodes the magnetic field and when it weakens, the star can no longer slow down its rotation speed and therefore the star remains at a rotation speed of 10-12 seconds.
Historically, scientists believed that radio pulsars (stars that can be detected using radio waves) had a limited rotation speed but could not explain this theoretically. The scientists thought that the limitation was due to an observational effect: the stars with low rotation speed are less luminous in the radio range and cannot be observed. "Space missions in the last decade have detected an increasing number of isolated X-ray pulsars, and to our surprise none of them have a rotation speed longer than 12 seconds, and so far there has been no satisfactory theoretical explanation for the phenomenon," concludes Nanda Ri, a researcher at the Institute of Space Sciences in Barcelona.
to the notice of the researchers
For information on the OPLI website
19 תגובות
deer
Thank you. I will try to look at the sources you referred me to as soon as possible.
sympathetic,
As for the classic effect you describe, I'm not sure that's true due to the electrical interaction that will try to balance the charge.
Moreover, this effect is true in a thermal gas, but in the case of particles at 0 temperature (a good approximation, because the temperature there is much lower than the Fermi temperature) it is not true - imagine non-interacting particles in a rotating orbit and held by gravity - in this case there will be no Any dependence between their trajectory and their gate.
About magnetars on Wikipedia (http://en.wikipedia.org/wiki/Magnetar) indicates that the source of the magnetic field is in the dynamo effect which has a conductive origin. As far as I know the matter is not agreed, but I may be wrong. Regarding superconductivity and superfluidity - I really don't understand these things (I only know as a slogan that it is considered a very complex subject because there is .... and also about fluidity and conductivity). As for the rotons you offer, read approx http://en.wikipedia.org/wiki/Neutron_star#Rotation About the glitch phenomenon - as far as I know, this phenomenon is often linked to the quantization of the vortices in a liquid (although I never understood how such quantization creates a macroscopic phenomenon).
deer
Regarding the question of the magnetic field, Tam asked: is it not enough that the star rotates so much?
fast to separate the electrons and protons due to their different masses,
Trivial classical effect. Regarding superfluidity and especially superconductivity. If the star is on a conductor
How the magnetic field penetrates through it. If it is a liquid, what is the mechanism of digestion
The star shines. In addition to superfluidity there is a speed threshold if the superfluid is moving too fast
Produces rotons according to the Landau dispersion relation.
sympathetic,
As for the question of what the magnetic field comes from - it is true that there are protons, but there are also electrons. As far as I know, the vast majority of models assume that the neutron star is neutral overall (also in all its regions) and therefore this explanation is not valid.
It may be possible to assume a certain charge distribution that will create effective currents, but you have to explain that and I'm not sure it's the smartest way.
Regarding the phase transition,
It is probably a transition to a more stable form in terms of energy / entropy - otherwise it would not have happened. The question is whether this story about pasta grains is indeed true. Note that the claim regarding pasta is not observational, but theoretical, so the explanation for this is clear - someone put certain conditions in his model (probably ran it on a computer...) and this is what he got - the question then is not "why?" but "is he right?".
Whether this model is correct or not, it is already beyond my understanding (and I think you can say our understanding) and this is what I meant by saying that finger waving will not help.
Neutron stars are very problematic animals:
A large part of the fundamental physics of the interactions is not clear there - it mixes nuclear physics in unknown domains with elementary particles in unknown domains. It is not clear which exotic particles (hyperons) exist there, and therefore it is also not clear which phenomena of condensed matter they will cause (if exotic bosons are there, for example, they may be found in the Bose Einstein state, but if they are not there, they will not be in this state - because they are not there). What is clear is that such effects cannot be ignored there - on liquidity that probably exists there and possibly on conductivity as well. To all this you will of course add general relativity which also contributes its part and you get very complicated things that at least I can't follow from beginning to end - I can at most focus on something and try to understand it.
Therefore, if there is someone who claims that it will become seeds in the form of pasta - blessed is the believer...
deer
Thanks for the correction I did think it was maximum speed. Regarding considerations and calculations
finger. First I think the magnetic field is simply due to the charge of the neutron star.
A star has protons and when they rotate they produce a magnetic field. Second, regarding speed
Minimal rotation or rather minimal magnetic field, I think the article implies
A phase transition that occurs in a certain magnetic field. My guess is that in a magnetic field
It is energetically better for protons and neutrons to get along in spherical symmetry
While in a weak magnetic field it is better in terms of entropy for the nuclei to arrange themselves in a structure
Pasta which has a higher entropy. I'd be glad to hear your opinion.
Ehud (and others),
Some order:
Note that the indicated barrier is on minimum and not maximum rotation speed, so it is actually related to weak and not strong fields.
I'll start with what I know
There is a known (and better known) barrier on maximum rotation speed - if the rotation frequency exceeds the root of G*rho, a classical body held by gravity alone will disintegrate. In a neutron star there are corrections (relativity and strong force), but in principle one does not expect neutron stars with a cycle time longer than an average of milliseconds.
The story here is different:
Suppose a neutron star has a magnetic field (and as far as I know the explanation for the origin of this field is not fully understood). The star rotates, and in the process radiates energy. For a rotating dipole the amount of energy that works for radiation is proportional to omega^4, on the other hand the amount of kinetic energy in rotation is I*omega^2 and time derivative we conclude that the time derivative of omega is proportional to omega^3. This means that very quickly, no matter what spin the neutron star started from, it will reach a state where it is difficult for it to slow down (because the dependence of omega_dot on omega is very strong). I have always understood that this is the reason why there are no neutron stars that rotate very slowly and according to the link here to the OPLI website, it is not far from the truth.
In conclusion (before what is said in this article):
Any problem you can explain with classical-relativistic finger gestures will amount to this: there is a limit to how fast you can spin (~600 times per second is the accepted number) and there is a practical limit in that it is difficult to spin slower than once every 12 seconds.
Now we come to the article
The new story here is, as I understand it, that they claim that it doesn't just stop at 12 seconds, but that there is some kind of phenomenon of pasta grains (something that probably won't emerge from finger calculations that any of us will do on talkback on this site) and they are the ones who set this limit - Ashari The believer…
deer
Thank you very much for the explanation!
In relation to the nuclear interactions the electromagnetic interaction
which originates from the magnetic field is a disturbance. Is at a certain final rotational speed
It can be estimated that the electromagnetic interaction becomes an order of magnitude
of the nuclear interaction? I would assume this is the reason for the speed limit
The round mentioned in the article. Another possibility is that the blockage comes from magnetic fields
So strong that they are able to produce pairs from the vacuum and this is where the barrier comes from.
I would love to hear your opinion on the subject.
Ehud and Neta:
Why don't neutrons decay?
The neutrons do not decay because the protons also decay. The simplest model for the nucleus of a neutron star speaks of a fermion gas consisting of protons, electrons and of course neutrons - all degenerate. From statistical considerations it is also clear that they all have the same Fermi energy (for temp. T=0 which is a good approximation for a neutron star, Fermi energy is the chemical potential). This is of course why neutrons do not decay - it will simply cost more energy. This model of a free fermion gas is obviously incorrect, in particular it assumes the absence of interactions between protons and neutrons and such reactions of course exist - this is the reason for the existence of nuclei.
Why are there kernels there?
Let's think about low-density matter (say in a room). If I collect protons and neutrons, it is clear that they would prefer to be in nuclei and not in separate particles - this is how they gain the nuclear binding energy. This is true at relatively low densities, and naively, by "low densities" it is meant in relation to the nuclear density. This means that at densities lower than the nuclear density, it is observed that at least some of the matter will be in atomic nuclei, and this is indeed what happens in the outer parts of a neutron star.
In order to model it relatively simply, a Fermi gas is assumed for the free particles (mainly neutrons and electrons at this stage), the neutrons also have the possibility of being bound to nuclei (the potential here is assumed to be known masses of nuclei), and then the chemical potential between the neutrons bound to the free neutrons is compared.
What you get is that up to approximately densities of 6^10*5 grams per cubic meter (neutron drip), there are no free neutrons at all. At higher densities, free neutrons begin to form and very quickly they control the pressure (and hence the model of free neutrons becomes effective at least in terms of the hydrodynamics of the star). Moreover, at high densities (high Fermi energy) it "pays" for neutrons to attach to very heavy nuclei, much heavier than iron - this is because they pay in an unstable nucleus but are more profitable in that they do not have to pay in free motion. This is how you get huge nuclei of hundreds of nucleons in the envelopes of neutron stars. Note that these are saturated with neutrons (because each proton is paid for with a free electron with high Fermi energy).
This simple model runs into several problems:
- It is not clear how such large nuclei behave, observational information is only available on much smaller nuclei and from there it is only extrapolations (although there is quite a consensus that the result will not be qualitatively different).
- The main problem is when you reach SDG densities of the nuclear density (the core of the star) - from then on the "free" particles are far from free - they experience nuclear interactions all the time and as you know, these interactions are far from being understood.
The article you read, Nissim, I did not read. And not a recipe to read. apperantly. But according to the statistics I'm just guessing,
What is written in the article - we will ignore your words.
Listen, Nissim: you don't seem to apply the advice you give to yourself.
I suggest you act differently than you are used to.
Don't be a fool, you have a lot more to learn and shut up and tell your friend. I'm not your friend And I don't care what you say.
Bottle
Actually not Wikipedia in this case 🙂
But why not slander if possible?? An article I read is http://arxiv.org/pdf/1111.3434v1.pdf
Shema Kabok - when you have nothing to say it is better to be silent...
They tried
Have you already received a thank you letter from Wikipedia?
sympathetic
I understood what you are saying. I found several sites that say the opposite ….. but also several sites that say the same as you. And the number of sites that say the same as you is greater.... 🙂
Miracles
Another lesson in science. It is true that the neutron has a magnetic field, but the neutron's magnetic field
cannot create a magnetic field for the neutron star due to symmetry considerations. The star is in the ground state like this
that the fermions (in this case the neutrons) were degenerate, meaning the same number of neutrons with
Spin in one direction like that in the opposite direction. Therefore the magnetic moment of the neutron cannot give
The neutron star has a magnetic field and needs protons.
Nte
You are right (by the way, I did not say that the neutrons and protons are arranged in nuclei).
I think the intention was that the arrangement of the nucleons in the star is not symmetrical
cell. The starting assumption was that the structure of the neutron star would be a spherical arrangement of
Neutrons and some protons but apparently the strong magnetic fields violate
this structure (this is my hypothesis regarding what is said in the article and must be addressed
to her with a limited guarantee). By the way, I wonder what prevents the neutrons from decaying into protons?
sympathetic
Regardless of what you said - the neutron also has a magnetic field...
Ehud is clear that something has to give the charge. It's just that there shouldn't be "atomic nuclei" but all the nucleons (protons and neutrons) should be "shoulder to shoulder" which should give crazy weight to a small amount of volume. Therefore, the reference to different atomic nuclei or their shape is not clear.
point,
how slow? Could it be that these things do not read?
Say point.com is your domain?
Nte
It's funny but it's a fact less known to the general public, a neutron star is also made up of protons
Otherwise there would be no magnetic field.
It can have a magnetic field
What does it mean "causes the nucleus of the atoms to line up in a non-spherical shape"?
A. in what form?
B. I thought the whole idea of a neutron star was neutrons stuck together like a giant nucleus made up of only neutrons.
Maybe neutron stars that slow down to more than 12 revolutions per second, collapse in on themselves and become a quark star or something?