Researchers suggest changes to theories regarding neutron star crust structure

Mar 27, 2014 by Bob Yirka report
Neutron star. Credit: NASA

(Phys.org) —A pair of researchers affiliated with universities in Sweden and Denmark has published a paper in the journal Physical Review Letters, suggesting that current theories that describe the makeup of the crust of neutron stars need to be rethought. In their study Dmitry Kobyakov and Chris Pethick have found that if the crusts of neutron stars conformed to current thinking, they would be unstable.

Neutron stars are the remnants of supernova after collapse—though small in size, on average just 20 kilometers in diameter—they are exceedingly dense with most having a mass greater than our own sun. Researchers are interested in because it is believed they may be the source of some gamma ray bursts and that they could also be releasing gravitational waves. To better understand such phenomena, scientists have been studying the crusts of neutron stars, which are believed to be just one to two kilometers thick, but which might hold the key to their behavior.

A neutron star's is believed to be made up of clumps of neutrons and protons that have been forged together by gravity, with nuclei that is believed to be neutron rich. Those neutrons in the crust that are not clumped together with protons, theorists have suggested, move freely about the crust but don't have much of an impact on the properties of the crust as a whole. In this new effort, the researchers suggest that if that were the case, the crust would be unstable, which means, they claim, that the free flowing neutrons exert far more influence than has been previously thought.

Kobyakov and Pethick propose that the free flowing neutrons and clumps can be thought of analogously to earthbound metal alloys—with neutrons and nuclei standing in for different atomic metal species. This would imply, the two suggest, that like metal alloys, the crust of a neutron star could have a number of different structural phases, each of which could have different properties.

Different properties in the crust of neutron stars could possibly help explain behavior that has been observed, such as gamma ray bursts—they could be the result of part of the crust shattering, much like some metal alloys when reaching a certain stress point. Such properties might also help explain what are known as "glitches"—where neutron stars suddenly, inexplicably begin to spin around faster. There is also the possibility that different parts of the crust with different structures could give rise to mountainous type terrain on the surface, which some have suggested might be related to the emission of .

Explore further: Simple, like a neutron star

More information: Towards a Metallurgy of Neutron Star Crusts, Phys. Rev. Lett. 112, 112504. journals.aps.org/prl/abstract/… ysRevLett.112.112504

ABSTRACT
In the standard picture of the crust of a neutron star, matter there is simple: a body-centered-cubic lattice of nuclei immersed in an essentially uniform electron gas. We show that, at densities above that for neutron drip (∼4×1011  g cm−3 or roughly one-thousandth of nuclear matter density), the interstitial neutrons give rise to an attractive interaction between nuclei that renders the lattice unstable. We argue that the likely equilibrium structure is similar to that in displacive ferroelectric materials such as BaTiO3. As a consequence, the properties of matter in the inner crust are expected to be much richer than previously appreciated, and we mention possible consequences for observable neutron star properties.

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cantdrive85
Mar 27, 2014
This comment has been removed by a moderator.
Maggnus
4.4 / 5 (14) Mar 27, 2014
"We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture." Hannes Alfvén

Voila! Imaginary conjecture...
Based on sound theoretical constructs built upon strong experimental evidence.

Unlike imaginary, never seen lightning bolts carving vast valleys in some imaginary fantasy world of an electricity based universe where the sun can be replaced by a planet 1/10,000th its size, and where gurus of this imaginary universe sit in caves and imagine what a wonderful universe that would be. No one could possibly be stupid enough to fall for that, could they?
hemitite
5 / 5 (4) Mar 27, 2014
What the article fails to point out, but can be gleaned by reading the abstract, is that the crust of a neutron star is thought to be composed of degenerate matter.

I think a better analogy for this sort of system would be the mineralogy of the earth's mantle where it is thought that changes in temperature and pressure can lead to phase transitions that are conjectured to be the mechanism for energy release in deep focus earthquakes.
cantdrive85
1 / 5 (11) Mar 27, 2014
What the article fails to point out, but can be gleaned by reading the abstract, is that the crust of a neutron star is thought to be composed of degenerate matter.

I think a better analogy for this sort of system would be the mineralogy of the earth's mantle where it is thought that changes in temperature and pressure can lead to phase transitions that are conjectured to be the mechanism for energy release in deep focus earthquakes.

Whereas a supposed neutron star is made of degenerate matter, so too is maggnuts but just a degenerate.
katesisco
5 / 5 (1) Mar 27, 2014
All of these adjsutments and Viola! a magnatar appears.
malapropism
5 / 5 (7) Mar 27, 2014
"We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture." Hannes Alfvén

Voila! Imaginary conjecture...

Well, the thing is, I'd love to see you (or Hannes Alfvén, who you're always quoting) do some experiments on a neutron star. Or even just on neutron star matter.

No, really. I would love it - I'd be amongst the first to clap and praise your success. Please publish.

cantdrive85
1 / 5 (9) Mar 27, 2014
"We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture." Hannes Alfvén

Voila! Imaginary conjecture...

Well, the thing is, I'd love to see you (or Hannes Alfvén, who you're always quoting) do some experiments on a neutron star. Or even just on neutron star matter.

No, really. I would love it - I'd be amongst the first to clap and praise your success. Please publish.


The neutron star is imaginary conjecture, why bother? Why not initiate a study on leprechauns? Or the Yeti?
cantdrive85
1 / 5 (7) Mar 28, 2014
never seen lightning bolts carving vast valleys in some imaginary fantasy world of an electricity

Well, we have not seen two planetary bodies approach one another have we. The idea that this can happen is not limited to EU, think moon capture. That being said, we have not seen two bodies such as the Earth and Moon collide then re-coalesce into solid bodies again, yet you believe that is viable. Let's apply the pseudoscience you understand, magnetic reconnection. I think the claim is when different two magnetic fields get near, the "magnetic field lines" break releasing energy only to "reconnect" with the other field lines. If the Moon had even a weak electromagnetic field, if it approached the Earth the same "magnetic reconnection" would occur. The two solid bodies would discharge directly however, just as happens when you get shocked from your door knob.
alfie_null
5 / 5 (4) Mar 28, 2014
Regarding the crust shattering mentioned in the article. I've got to wonder what the "mountainous type terrain" on the surface is like. I can't imagine the mountains are anything like what we know as mountains.
Maggnus
5 / 5 (5) Mar 28, 2014
The neutron star is imaginary conjecture, why bother?
Because there is good, strong mathematical theory suggesting they can occur in nature, and this is backed by strong observational and experimental evidence suggesting that such objects exist. I know that's a bit hard for you to understand, tucked away in your cave and all, but that's how REAL science works.
Why not initiate a study on leprechauns? Or the Yeti?


For the same reason they don't study EU; just like EU, they are fictional constructs based on superstitious flights of fancy arising from imaginary myths and legends.

Mind you, I would give more support to the study of Yeti than the study of the quasi-religion that is EU; at least there is some scientific basis for its existence!

Maggnus
5 / 5 (3) Mar 28, 2014
Regarding the crust shattering mentioned in the article. I've got to wonder what the "mountainous type terrain" on the surface is like. I can't imagine the mountains are anything like what we know as mountains.
WHy not Alfie? I mean, mountains are the result of up-thrusting by plates, (well, and the the left over debris of meteorite impacts, bt that really doesn't apply here) and if you think of the crust and fractured, then coming against each other in a similar manner to plates in tectonic theory seems reasonable to me.

Although, the more I think about it, the more I see what you mean. I don't imagine they could get very big, if they exist at all.
cantdrive85
1 / 5 (5) Mar 29, 2014
Because there is good, strong mathematical theory suggesting they can occur in nature, and this is backed by strong observational and experimental evidence suggesting that such objects exist.

Only in the fanciful minds of pseudoscientists. There is actually not one iota of experimental evidence, and what observational evidence exists in no way supports the claims being made. The same skewed knowledge of physics that makes them ASSUME they are looking at BH's lead to the same skewed assumptions they are looking at these abominations of physical laws.
Tim Thompson
5 / 5 (1) Apr 06, 2014
The neutron star is imaginary conjecture, why bother?

Hogwash. See Baade & Zwicky, 1934 and Oppenheimer & Volkoff, 1939
http://adsabs.har...46...76B
http://adsabs.har...55..374O

Baade & Zwicky predicted the existence of neutron stars based on their observations of supernovae, and Oppenheimer & Volkoff proved the fundamental stability of a neutron star. There is in fact copious observational evidence that neutron star exist, especially in binary systems where masses are easy to determine, or for flaring objects.
Tim Thompson
5 / 5 (1) Apr 06, 2014
The same skewed knowledge of physics that makes them ASSUME they are looking at BH's …

Also hogwash. When matter falls onto anything it will hit a hard surface and detonate, visible as an X-ray flare, *except* in the case of a black hole (BH). Since a BH has no hard surface, matter simply falls through the event horizon and disappears. One can predict how the flaring differs for these two types of objects and determine whether or not a solid surface is present; if not, we have a BH. One can also detect the disappearance of thermal emission. As shown below, there is significant observational evidence for event horizons and therefore black holes.

http://adsabs.har...46..407R
http://adsabs.har...15..402M
http://adsabs.har...92L..63P

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