The upper crust of a neutron star is thought to be composed of crystallized iron, may have centimeter high mountains and experiences occasional ‘star quakes’ which may precede what is technically known as a glitch. These glitches and the subsequent post-glitch recovery period may offer some insight into the nature and behavior of the superfluid core of neutron stars.
The events leading up to a neutron star quake go something like this. All neutron stars tend to ‘spin down’ during their life cycle, as their magnetic field applies the brakes to the star’s spin. Magnetars, having particularly powerful magnetic fields, experience more powerful braking.
During this dynamic process, two conflicting forces operate on the geometry of the star. The very rapid spin tends to push out the star’s equator, making it an oblate spheroid. However, the star’s powerful gravity is also working to make the star conform to hydrostatic equilibrium (i.e. a sphere).
Thus, as the star spins down, its crust – which is reportedly 10 billion times the strength of steel – tends to buckle but not break. There may be a process like a tectonic shifting of crustal plates – which create ‘mountains’ only centimeters high, although from a base extending for several kilometres over the star’s surface. This buckling may relieve some of stresses the crust is experiencing – but, as the process continues, the tension builds up and up until it ‘gives’ suddenly.
The sudden collapse of a 10 centimeter high mountain on the surface of a neutron star is considered to be a possible candidate event for the generation of detectable gravitational waves – although this is yet to be detected. But, even more dramatically, the quake event may be either coupled with – or perhaps even triggered by – a readjustment in the neutron’s stars magnetic field.
It may be that the tectonic shifting of crustal segments works to ‘wind ‘up’ the magnetic lines of force sticking out past the neutron star’s surface. Then, in a star quake event, there is a sudden and powerful energy release – which may be a result of the star’s magnetic field dropping to a lower energy level, as the star’s geometry readjusts itself. This energy release involves a huge flash of x and gamma rays.
In the case of a magnetar-type neutron star, this flash can outshine most other x-ray sources in the universe. Magnetar flashes also pump out substantial gamma rays – although these are referred to as soft gamma ray (SGR) emissions to distinguish them from more energetic gamma ray bursts (GRB) resulting from a range of other phenomena in the universe.
However, ‘soft’ is a bit of a misnomer as either burst type will kill you just as effectively if you are close enough. The magnetar SGR 1806-20 had one of largest (SGR) events on record in December 2004.
Along with the quake and the radiation burst, neutron stars may also experience a glitch – which is a sudden and temporary increase in the neutron star’s spin. This is partly a result of conservation of angular momentum as the star’s equator sucks itself in a bit (the old ‘skater pulls arms in’ analogy), but mathematical modeling suggests that this may not be sufficient to fully account for the temporary ‘spin up’ associated with a neutron star glitch.
González-Romero and Blázquez-Salcedo have proposed that an internal readjustment in the thermodynamics of the superfluid core may also play a role here, where the initial glitch heats the core and the post-glitch period involves the core and the crust achieving a new thermal equilibrium – at least until the next glitch.
How can you show a picture like that and not tell us what ‘nuclear pasta’ and ‘proton drip’ are? No fair!
I know, I know, Dr Google, Prof. Wikipedia, etc…
I never realized how much of horizontal structure is caused by plate tectonics until I started to read about it. On Earth overthrusting is part of a characteristic structure extending on the order of hundreds of kilometers.
In fact, I believed that the small scale deformation of older Archaean rock was caused by stresses over time. Turns out that more importantly older Earth plate tectonics has another mode with more vertical gravitationally driven “sagduction” buckling deformation, which may extend on the smaller order of tens of kilometers.
This story so much brings to mind a certain series written by Robert Forward. Rest in Peace “Bob”.
vagueofgodalming, it may be because the subject was raised in another comment thread. This reference was given, and may help. (I haven’t read it through yet.) In any case it describes ‘nuclear pasta’ and ‘proton drip’.
It is from Prof. Miller, btw. 😀
Heh. You successfully fooled me – it’s “neutron drip”, of course.
Nice well written and informative article to chew over.
BTW: Para 1 ‘ which may proceed’ – ‘precede’
Steve you wrote that – “All neutron stars tend to ‘spin down’ during their life cycle, as their magnetic field applies the brakes to the star’s spin.” – And this is because of the neutron star’s dense magnetic field is entangled with the galactic magnetic field.. right?
Thanks AndyInv – I have successfully reversed the arrow of time so that my spelling now precedes your correction. However, if you have any other suggestions to offer, please proceed.
@ vagueofgodalming
Sorry for jargon.
The nuclear pasta idea relates to the geometry of nuclear material under extreme gravitional or magnetic stress (and perhaps other stressors I haven’t thought of).
Rather than adopting the spherical geometry of the standard model for an atom – nuclear pasta may appear flattened (fettucine), tubular (penne), layered (lasagne) or stretched out (spaghetti).
Neutron drip refers to the instability of certain nuclear forms. Under extreme gravitional pressure, introducing an additional electron into a nucleus will cause it to combine with a proton – forming an extra neutron.
And (OK, more jargon) once the neutrons in an atomic nucleus are filled to an energy level equal to the rest mass of a neutron, any further neutrons formed cannot be bound within the nucleus – so they ‘drip’ out.
In other words, don’t overcook your pasta or it will go all soggy and your dinner party will end in tears.
According to the calculations i just did in my head
1 cc of a NS wieghs about the same as 50 queen
marys Amirite ?
Steve Nerlich wrote: In other words, don’t overcook your pasta or it will go all soggy and your dinner party will end in tears.
It must mean that neutron stars are the vacation spots for the flying spaghetti monster. 🙂
All of these structures are new to me as well. We might not be so surprised. I was aware of the outercrust of degenerate iron, similar to the interior of white dwarf stars. I always assumed that the body was a gas of neutrons, with a core of higher mass hyperon particles or a quark-gluon plasma.
LC
@Lawrence B. Crowell
Something commonly overlooked is that although the galactic magnetic field is not very strong, due to its overall size it is actually quite powerful and its influence therefore tends to be underestimated. The IBEX (Interstellar Boundary Explorer) mission has shown that the galactic magnetic field may have far more influence than previously assumed.
http://www.bu.edu/phpbin/news/releases/display.php?id=1936
Given that Neutron stars create a HUGE magnetic field, its interface with the IMF may play a major role in deceleration of rotation in those stars.
Aqua,
The magnetic field of the neutron star over time transfers the angular momentum of the neutron star to external material. The galactic magnetic field is in the nano-Gauss range, which is not enough to have much effect.
LC
My point exactly.. “The ‘external material’ the star is braking against includes its own stellar wind of charged particles.” oTay then.. WHAT causes that stellar wind to not rotate along with the given star? You are saying its angular momentum, I’m saying, its that AND the interface with the IMF.
This article really highlights the utter strangeness down in the extreme parts of the universe.
Pasta Topology . . . New field of study
Nice article!
Aqua:
Like, err… about as much influence as a drizzle has on a speeding freight train, dude.
@ Aqua.
Lawrence B explains it well.
Here the ‘skater spreads arms out to slow down’ analogy fits. I mentioned this in last week’s AWAT (Making Sense Of The Neutron Zoo). The ‘external material’ the star is braking against includes its own stellar wind of charged particles.
I understand that the Sun’s spin is gradually slowing for much the same reason. This is largely why the Sun contains 99.9% of the solar system’s mass, but only 2% of its angular momentum (what happens after 5 billion years of magnetic braking).
@Aqua, you are joking right?
If I rotate around my axis and shoot a bullet, you claim that the bullet will rotate around me?
The solar wind is just a bullet being shot from the Sun. Only close to the sun it might get caught in the magnetic field of the sun but once it clears there is no more force acting on it from the Sun itself.
The only thing that an ejected charged particle will do once it clear the Sun’s surface and far enough from the Sun outside the magnetic loops is wiggle a bit because of interaction with some very close nearby other charged particles a few meters away but that is all.
@Steve Nerlich
You say it is braking against it’s own solar wind and charged particles.
The question Aqua probably does not dare to ask, is how far from the stars surface is this effect? Are we talking about a few star radii? Some AU? Or light years?
To have some sense of scale of our Sun.
The sun loses on Earth mass every 150.000.000 years.
About 0.01% was lost in 4.570.000.000 years.
0.01% / 4.570.000.000 = 2.18818*10^-12 %/year
0.000 000 000 000 218818% per year! in a basically 180×360 degree. Solar wind does not have the power to move a fly at Earth’s distance!
Don’t confuse solar wind with the energy in photons. Solar sails use LIGHT energy (E=mc^2) NOT solar wind. Light can push a 1 Kg Mass if you have 1 square KM solar sail. The solar wind charged particles is 5000 times lower than this.
Now you wonder why EU/PC people never dare to use numbers. On Earth the effect of light is 5000 stronger than their charged particles in solar wind!
Oops… my bad. Dyslexic I’m not.
What I meant to say was: “WHAT causes that stellar wind to rotate along with the given star? You are saying its angular momentum, I’m saying, yes its that, AND the interface with the IMF acts to brake that motion.”
On the Sun and magnetic braking theory go here:
http://en.wikipedia.org/wiki/Magnetic_braking.
While solar wind particles are still in proximity to the spinning Sun, its magnetic field lines are proposed to give the charged particles an extra push (i.e angular momentum), so that they shoot away in an arc.
A distance of nearly 3½ times the radius of the Sun is proposed for the effect to be of significance.
@ Aqua
As the article you linked to suggested, most of the interaction between the solar wind and the IMF is happening at the heliopause (i.e. that’s ‘the interface’).
Hard to see how this could feed through to influence solar wind movement at closer proximity to the Sun?
My thanks to everyone. The main reason I like this site is because there is an effort to clarify and share information. Most of the participants are quite forgiving of my sometimes under-informed meanderings. I must confess that I have occasionally used those meanderings to ‘pry open’ a subject for the sake of prodding a learning experience from and thru the participants.
Of course there are always those whose comments come from a less than congenial attitude and whose agenda’s include ego gratification rather than the sharing of information.
This has been been nicely untangled in the thread, but I have some specific comments.
First, a nitpick. “Entangled” becomes overloaded with the QM technical term which is a different phenomena, and since there are alternatives why not use them for clarity and so “physicity”? Plus, “tangled” is shorter.
Second, as magnetic fields (B) go as r^-3 in strength at best (from dipoles), you don’t expect to see much B-B interaction and I don’t think you do. Most of the time B fields interact (and dissipate energy) by other means, from simple induction up to, apparently, fancy magnetic braking.
Third, I don’t know how you envision tangling here. Magnetic fields are still fields, and obey superposition of (field from) charges. [Long discussion on magnetic field vs sources and sinks, and so charge densities in vacuum vs materials, omitted here.] No extraordinary tangle or dissipation effects here that I know of. On the contrary, energy conservation preserves charges and so fields.
However, when they couple to a plasma things becomes different. The synchrotron movement of charges along magnetic lines breaks conductivity symmetry, with virtually no resistance along the field and high resistance in other directions.
This asymmetry couples back to the field in such a way that field lines become preserved. The plasma shores up the field as it streams, fluid like in the MHD approximation, along the lines. Here magnetic field lines can tangle and be kept that way.
There are also mechanisms such as magnetic reconnection that let different magnetic domains of the plasma interact and dissipate energy in the process, so that could feasibly fit such a tangle picture.
But if there is no sufficiently dense field and perhaps more importantly here between star and galaxy no sufficiently dense plasma, there are no such tangles.
I have many times wondered what particles are most responsible for the magnetic breaking of a neutron star. I know the neurton star itself provides some, and that the ISM can provide some, but wich is the strongest contribution.
@Aodhhan
A quick peek here at the section entitled “structure” will shed a brief light on the current thinking and competing models. There is also a useful discussion at Astronomy Cast episode 38 Neutron stars and their exotic cousins. Hope this helps.
“energy conservation preserves charges” – I think I could have worded that better. YMMV.
I’m having a really hard time buying the de-formation of an atom to such a degree. Basically, this means there is enough heat and pressure to overcome the 2nd strongest force in the Universe. Something we know gravity is far far far far far ^9999999…9 weaker than.
Likely the atoms are being “scrunched” into a lattice of some sort (ie carbon to diamond) to fill every bit of free space. However, I’m not buying the fact there is enough gravity and heat to force electrons closer to the nucleus.
I might be able to buy the electron is being forced a “bit” closer to the nucleus, but not enough to have a hugely deformed orbit. More likely it is scrunched a bit more, but equally, such as a snowball being packed.
…since there is only so much the atoms can be compressed and heated, they are likely losing their electrons at times, and therefore theoretically losing other atomic particles…thus we have radiation…. and very energetic radiation at that.
To deform an atom so much, would require enough heat and pressure, you are just a bit away from fusion. Obviously there isn’t enough evidence of this. I doubt there is even enough heat & pressure for iron to form into other elements… and this would happen before spaghetti-fying atoms.
Someone convince me otherwise. 🙂 Gonzolez-Romero & company havn’t put out enough information to do it.
@Aodhhan,
You do realize that this article is about a “neutron” star? And a “neutron” star is a teeny weeny bit less massive than a black hole.
Unless you also believe that a black hole has its atoms intact, just squeezed a bit tighter than a neutron star?
It is clear there is a great deal of confusion here. A neutron star forms for a star greater than 1.4 solar masses. This is the Chandrasekhar limit, where the internal pressure is sufficient to fuse electrons with protons so the body’s interior is constituted largely of neutrons. There are these additional complexities of a degenerate iron crust and this “pasta” outer mantle. Further in to the interior for a mass near the Chandrasekhar limit there might be more exotic states of matter, such as hyperon particles or maybe a quark-gluon plasma.
The magnetic field of a neutron star slows down the rotation by inducing an EMF on matter outside. If the magnetic field (B field) were perfectly dipole and aligned absolutely with the rotation of the neutron star the B field would do nothing. But if it is not so aligned and if it has higher moments then a nearby region with charged particles will experience a changing magnetic field dB/dt, which is equal to the electromotive force dB/dt = emf, and so the energy of the rotating neutron star body is transferred into currents, and angular momentum is transferred as well.
A black hole occurs with a the breakdown of a second Chandrasekhar limit, where the Fermi statistics of the neutrons is no longer able to support gravitational collapse with this degenerate pressure. The collapse is complete and the body falls towards an event horizon and disappears.
LC
Please learn something about stellar evolution guys… Much of what is being said here is mostly quackery. (or is that now known as quarkery?)
I.e. “Likely a neutron star transfers angular momentum to the galactic disc until losing its magnetic field, gravity collapses it into an electron star, which will collapse into a black hole. ”
Please. What does this rampant gobbledygook actually mean here?
Aodhhan here really should learn something about basic quantum mechanics.
Matter is not like solid spherical balls but is instead mostly empty space that act under the strong and weak forces, behaving in the highly energetic quantum background under quantum field theory.)
As for neutron stars.
The mass of a 5 kilometre neutron star is between 1.4 and about 2.5 solar masses, whose escape velocity is about 100,000 km.sec^-1. (Some say the upper limit is 3.0 solar masses, but is assumed as ‘stationary’ mass.) The upper range is near the so-called the Tolman-Oppenheimer-Volkoff Limit, where the fluidity of the neutrons stops and its degeneracy pressure is overwhelmed – leading to theoretical quark stars or black holes. Nearly all neutron stars are rapidly rotating and oscillate / vibrate (milliseconds to about to about a minute) due to the strong gravitational forces acting on them.
Aqua said; “Of course there are always those whose comments come from a less than congenial attitude and whose agenda’s include ego gratification rather than the sharing of information.”
Damn right. Truer words were never spoken!
“The mass of a 5 kilometre neutron star is between 1.4 and about 2.5 solar masses”
Which gives a atomic area ratio of about 2.8k to 5, right?
Thanks Hon. Salacious B. Crumb for the exact term, Tolman-Oppenheimer-Volkoff Limit, for the breakdown of Fermi-degenerate pressure for neutron stars. I couldn’t remember the name and was too lazy to look it up. From a basic physics perspective it is a variant of the Chandrasekhar limit.
LC
wjwbudro
Good question! Depends if the neutron star density gradient is fixed or if it rises differently with bigger the neutron star.
The general five kilometre radius is the least known parameter, mostly due to the behaviour of material in the centre and at the surface. Moreover, the “observed” mass itself is subject to gross relativistic effects. (Some newer models suggest 20 and 30 kilometres, but all these are also quite uncertain.)
As far as I now, there is little evidence to say the diameters of neutron stars are significantly different in size – only different in densities (c.20). My understand says all neutron stars are about the same size and is not dependant on the mass! (So obviously common sense when applied neutron stars is not very clear cut!)
My answer to you question would be no.
I’ll try again. (Press the submit comment too soon!)
wjwbudro
Good question! Depends if the neutron star density gradient is fixed or if it rises differently with bigger neutron stars.
The general five kilometre ( ten km. diameter radius is the least known parameter, mostly due to the poor knowledge of the behaviour of material in the centre and near the surface. Moreover, the “observed” mass itself is subject to gross relativistic effects. (Some newer models suggest diameters of 20 and 30 kilometres, but all these are also quite uncertain.)
As far as I now, there is little evidence to say the diameters of neutron stars are significantly different in size – only differences in densities (c.20%). My understand says all neutron stars are all about the same size and that it is not dependant on the mass! (So obviously common sense when applied neutron stars is not very clear cut!)
My answer to your question would be no.
A thimbleful of neutronium, would weigh over 100 million tons on Earth. That’s 200,000,000,000 pounds! YIKES! (The ‘fat lady’ has indeed sung the blues!)
I find it VERY difficult to get my mind around this. Am I alone in that? It seems to stretch our ability to visualize the implications to the breaking point(?) as has been made obvious by some of the statements in this long blog. This innate ‘frustration’ seems to transform itself into personal attacks somehow – rather a transmutation of intelligence into a mentally unstable goo. An intellectual ‘black hole’? LOL!
Never-the-less, a good mental exercise stretches one’s imagination. If any of us learn something from this exercise, then it was worth the effort. My thanks to Mr. Nerlich for his ‘stirring of the ‘neutronium soup’.
@ Aodhhan
Is Lawrence B. Crowell not enough any more? Do you attack everyone, now?
Btw: Neutron Stars are in a diameter range of, say, 10 to maybe 30km. It doesn’t really matter, since compared to the hundreds of thousands of kilometers of normal stars this is extremely small. That is why one can say Neutron Stars are all of roughly the same size.
FYI: You said something that you wonder if gravity has become strong enough in a NS (Neutron Star) to overcome the Coulomb force. Gravity does not need to overcome the Coulomb force, and that is because electrons and protons attract each other, so they come together quite naturally. As a matter of fact, in a classical sense an atom cannot be stable. And why is that? Assume the electron would circle the proton (the nucleus, but let’s take hydrogen for simplicity), and the centrifugal force would thus equal the Coulomb attraction. What we know from (classical) electrodynamics (you can read that up in any textbook on electrodynamics; if you like a recommendation, Griffiths’ “Introduction to classical electrodynamics” is really good!!) is that an accelerated charged particle radiates (cyclotron or synchrotron radiation). Therefore, an electron circling a proton radiates! It has to! This means, it loses energy and will bend inwards. The electron will spiral inwards and will finally merge with the proton to form a neutron.
From this perspective (the classical one) it is not clear why matter and atoms are stable. The answer comes from quantum mechanics that forbids fermions in the same place with the same configurations (Pauli’s exclusion principle).
However, in normal quantum mechanics gravity is not accounted for. This is due to the fact that gravity is indeed so much weaker than the other forces.
However, in a NS things get different. Gravity has become much more important, now. And then you encounter such weird effects that the wave-function of the electrons suddenly overlaps with the wave-function of the proton/nucleus. This means they have a probability of being at the same spot at the same time that is not zero any more, which results in the merger of the two to become a neutron.
This is, of course, a very simplistic explanation, and I don’t know the whole details which must take the weak interaction into account. Nonetheless it is possible.
So, why are you ranting against everyone here?
DrFlimmer,
Aodhhan is trolling. He has claimed to have taught physics but that’s not the impression I’m getting based on his posts. It’s best to leave him alone. He should look up the theories behind neutron stars if he has questions about their existence.
I actually don’t care about Aodhan, his physics seems to get stuck around 1905. Within his way of thinking it might make sense, but neutron stars and black holes clearly shows that even though gravity is pretty weak it can actually crush atoms for real.
But I have a question, those neutron stars rotate very fast and has tons of magnetic fields and even plasma flying around.
May I assume that strange stuff happens because the magnetic field needs time to reach a certain point because of the limitation of the propagation of the waves to c? A bit like gravity waves but in this case magnetic waves?
@ ND
Most likely, you are right. 😉 Well, in fact, you are!
@ Olaf
This is definitely correct. Until a certain point the magnetic fields “bending” outward can follow the rotation of the inner field and (of course) the neutron star. However, when the velocity in direction of the rotation (well, the angular velocity at some distance from the neutron star) of a certain field line exceeds c, it cannot follow immediately any more and stays behind. The inner region (where the following is no problem) is sometimes referred to as the light cylinder (IIRC).
I admit that I haven’t dug deeply enough into this matter, so I can’t tell you what “strange stuff happens”. The field lines will wind up in some form, of course, maybe they will recombine from time to time, which could lead to powerful outbursts. But this is just what I guess — an interesting topic, no discussion on that!
Btw: This is also related to relativistic jets, because there the magnetic fields are also wound up and become twisted, probably because at one point they become larger than the light cylinder. I read a paper about it a few month ago, but since it contained too much information for me at that time (and, again, I didn’t dig deeper!) I cannot tell you much about it!
Aqua,
The atoms you’re made of are mostly empty space. And no I’m not trying to insult you with that 🙂
@DrFlimmer, Olaf and all.
If the “magnetic field needs time to reach a certain point” then wouldn’t the intense gravity and fast rotation of Neutron star change the time by changing the distance to that point via the Lense-Thirring effect (aka Frame Dragging)?
IIRC, one result of the Lense-Thirring effect is that light travels a little faster around a massive rotating body when moving in the direction of rotation and slower if moving against the direction of rotation.
The Lense-Thirring effect is of course usually very weak in normal circumstances. For example a rotating massive body such as the Sun is enough to shift the orbital period of Venus by only 0.0004 ± 0.0001 arcseconds/century.
However the higher gravity and faster rotation rate of a Neutron star should produce a much stronger Lense-Thirring effect particularly when measured closer to the surface thereby changing the distance travelled to a “certain point”.
Just asking …. as find information and results seem a bit scarce.
Thanks in advance for any feedback,
@ Aqua
Well, I think, no one really can grasp how nature works in one way or another. Our formulas are fine and work quite well, but to translate them into words that out brain can understand and visualize is almost impossible. I cannot imagine 4 dimensions, nor can I imagine what it really means that something only has a probability to be here and not there, or to be here AND there at the same time. Nature is weired, and the universe is even weirder than we can possibly imagine.
That’s why we keep going 😉
@ TerryG
Relativistic effects definitely play a role, and maybe Lawrence B. Crowell can give us some insights into it, since he is a real expert in that field.
The Lense-Thirring effect (or easier described as frame-dragging) swirls spacetime around a massive rotating object. Some people (I give here credits to Phil Plait) compare it to a waterfall, which is quite a nice analogy.
It will surely have an effect on the “strange things” that happen around a neutron star, but since I am not an expert here, I don’t want to start guessing what the results could be.
Folks, let’s try to be nice, shall we?
I’ve removed several recent comments that clearly violate our comments policy.
Thanks for the deletions.
Really, Aodhhan comments should have been removed in the first place, but I damned if I am going to be unjustifiably and openly bullied, be accused of plagiarism, or told my honest opinion is all just “cut and pasted.”
Saying “Folks, let’s try to be nice, shall we?” just assumes the protagonist is is equally guilty as the instigator. In this case, someone had to stand up this bad behaviour – something that has been symptomatic behaviour towards me and Lawrence by this individual.
Correction. This should read.
“Saying “Folks, let’s try to be nice, shall we?”, just assumes the protagonist is is equally guilty as the victim.”
@ TerryG: Neutron stars and black holes will have large frame dragging physics, or Lense-Thirring effects. These effects do only become large as one gets close to the gravitating body. Observing up that close is so far not possible. Yet in principle frame dragging should be observable, and the next decade may provide the tools to do this.
As for Aodhan, he is nuclear trouble. I will often avoid writing anything on a page where he has previously shown up.
LC
@ND – “The atoms you’re made of are mostly empty space.” Indeed… now if my body were made of Neutronium it would be a different story and I’d be one heavy dude! Oui? I’m so glad that’s not the case, AND that my spouse still finds me attractive! ~@; )