You know how they say that white dwarf and neutron star stuff is super dence because of the stars gravity... Well, I've always wondered if you could bring some of it back here on Earth, would it still stay super dence or would it expand back out to it's normal density once it was no longer in a strong gravity field?  Sort of like a sponge that you compressed with your hands and then let it go.

They should have an Ask Astro section in the forum!

I think you got the answer there, the material is condensed because of the ultra strong force of gravity in their natural states, and, removing that, should push back out to their 'normal' state so to speak.  The neutronium stops the gravity in a narrow range, any more outside pressure from material in a gravitational field will condense it into freefall and collapse to a singularity (black hole).  so, the state of neutronium in a neutron star also includes the pressure back against the gravity, which for stars of certain mass after explosion can perch on that narrow ledge of inward momentum sucessfully.  If we remove one force (gravity) the other outward force is still there as it had been while condensed, and that should rather suddenly succeed in reexpanding.

how big would the oceans be if we took out all the sponges??  oh wait thats off topic...

LOL

jerry

Hey thanks !   I found that I had posted basiclly the same question over a year ago and forgot about it. The topic was titled neutron star stuff. Anyway the answer I got there was that it would expand back somewhat but not back to the way it was before it was crushed because the basic structure of the atoms was destroyed... Oh who knows really I guess..  Think it's probly one of those things my simple little mind won't be able to really understand!!  Well if I had a piece of it here I'd probly poke at it with a stick to see what it does!!!

Hey now, that sponge thing got me thinking....  If the ice caps keep melting and the sea level keeps rising, maybe we could throw a bunch of sponges in the ocean to counter act it!!!   

quarkstar wrote:

how big would the oceans be if we took out all the sponges??

Where's Noah when you need him?

Naw, really...I'd agree with you.  If the gravity is no longer present, then unless the matter formed some kind of bond from the pressure, it would probably expand back to it's original state.  If it did form a bond, wouldn't it burst from the expansion? 

The neutronium question is interesting, but in my humble opinion, a question without an answer.

A neutron star gets smaller, the more mass it has. A typical neutron star has a 10 - 20km radius and a mass between 1.44 and 5 times the mass of our sun. If it had any less mass it would be a white dwarf, and any more mass would mean it would gravitationally collapse into a black hole.

So.. question 1. How much neutronium did you want to "bring back here on Earth"?

If it's less than 1.44 solar masses, then it would cease to be neutronium. It would be matter from a white dwarf instead The 1.44 solar masses of neutronium (the minimum amount) would have a radius of around 20km.

So put simply, if you want to bring back a box of it, you can't!

Question 2. So lets say you want to bring back the least amount of neutronium possible (1.44 solar masses). You need something to carry it in..   What would it be made of?

In order to carry around a neutron star, you would need something more dense?

You cannot "carry" neutronium around in anything, therefore the question is ... well...  pointless?

Okay, good point.  So let's rephrase the question then....Hypothetically speaking, if there were a way to bring neutronium back to earth in a box or something of the sort that could carry neutronium, and you wanted to bring 1.44 solar masses of it and you had a transport with a hold at least 20km wide, long, and deep, what would happen to the neutron star? 

 

Seriously, though.  To answer that question (at least attempt one), wouldn't it just exist as-is?  I mean, gravity is what holds the neutron star together, and with a mass of 1.44 solar masses it has the gravity to sustain itself, right?  The only way that the neutron star would expand is if somebody suddenly "turned off the gravity".  Which, if that were even possible, you'd just have a massive explosion on your hands. But in order to get rid of the gravity or to reduce it, you'd have to get rid of or reduce the mass, making it not a neutron star anymore, as was stated.  IOW, where the neutron star goes, so does its gravity...

Am I even understanding the question right, or am I just totally way off in left field here?

Yes, wherever the neutron star goes, so does its gravity.

But I think the only thing massive enough to "move" a neutron star would be...  a black hole. 

And, if somehow you managed to isolate and extract a few grammes of neutronium from it (theoretically of course!) all you would end up with is a broken box and some loose hydrogen

Well ummm...... I wasn't meaning bring the whole star back here!  It was a what if kind of question. And yes I know it would be impossible to bring a small piece back. You would be torn appart on the way down, fried to a crisp, and then smashed flatter than flat on the surface. Not to mention that there is nothing dencer you could use to cut a piece off the star if you could somehow avoid all the above getting there.....   Just a what if you could magicly make a teaspoon size piece of neutron star stuff appear in your lab.  Would it remain in it's super dence state or expand??  Oh and lets say the sample is at room temp too, don't want anyone telling me it would melt the whole planet or something!!!

So far I think the best answer I got was from demonstar under the topic" neutron star stuff".   He said he thinks it would expand somewhat but not all the way back to normal because the basic structure of the atoms were destroyed...Anyways, most of the answers I got was that it would expand back in some way.   And just because you don't know the answer dosen't mean it's a pointless question.

Oooohhhh....I see.

Okay, in that case, I'd agree that it would expand, but I think Speedfreek is right about one thing--it wouldn't be neutronium anymore, because of the lack of required mass, thus gravity.  I don't know about the atoms thing...Not that far into astrophysics quite yet.    So, I don't know....

I stand by my last reply. You would end up with a broken box (split by the pressure differential) and some loose hydrogen. ;-)

What I meant by that is the box you collected it in would split apart due to it's expansion, and it would expand back to the natural state of the matter for the environment it is currently in.

In the centre of a star the pressure causes the thermonuclear reactions that cause the star to shine... in your lab no such conditions would exist and it would expand and break down into it's constituent components.. i.e. mostly hydrogen.

I don't think it really matters that the atomic structure may have been destroyed when it was neutronium. Atoms tend to follow the natural laws of physics when in natural conditions.

I didn't quite say it was a pointless question because I couldn't answer it (well, almost!). I meant the original question as it stood had no real answer as it couldn't possibly happen, and after considering all the issues involved I asked you to consider if pointless was a good way to describe it (notice I put a question mark after pointless).

But all in all, yes it would "expand", although maybe not back into what it was before it was neutronium, but into what it would normally be if it was in your lab.

lynxcat wrote:

Anyway the answer I got there was that it would expand back somewhat but not back to the way it was before it was crushed because the basic structure of the atoms was destroyed

Thats a very good point and i'd overlooked it.  i would think, that, in a neutronium soup, solid or not, there would be little free electrons as the object wouldnt particuarly have to be charged in the first place.  we call it neutronium because the Fermi gas i think its called really has protons that absorbed eletctrons and an antineutrino and a gamma ray if i remember right how it (free neutron) breaks down..  but, i had thought, by proximity, that the neutrons would under loss of pressure, turn back into protons and electrons pretty quickly.  but since i'm thinkng about it.. a neutron has an up down down quark makeup.  a proton has an up up down quark makup.  somewhere in there, the breakdown of a neutron into an antineutrino and an electron and a gamma ray converts a down quark to an up quark, and yet, these three quarks and their gluons would remain in their triplet proximity, so that protons would indeed reappear.  i think the process might take more time than an explosion due to the halflife of a free neutron, but this is exoitic material and this is my first thoughts about it.  the electrons are emitted at some velocity i dont recall if they are near the speed of light or reasonably slowly.  they would i'd think, being close to its paired proton, orbit the proton directly, but it may travel to a nearby proton or not so nearby proton before being captured.  at the same time, the protons are popping like popcorn out of the neutrons, and are in close proximity, so they will attempt to separate from each other due to electromagnetic charge.  i guess this will produce a hydrogen ball, and not just instantly, but maybe fairly quick.. a few seconds versus a tenth of a second, or even some minutes versus a second. i dont have a reaction rate for Fermi gas neutrons because they may not be actually considered free neutrons and have the free neutron halflife of what is it something like 15 minutes for half the sample?  now, since this is a collapsed star that is NOT a collapsed ball of hydrogen to begin with, there will be some extra neutrons as most isotopes of most elements likely to be anywhere near inside a supernovae remnant are going to have the typical few extra neutrons in them, so, i'd suspect there should be free neutrons left over.  those would likely turn into hydrogen being that they're the leftover ones.  but what of interior particles closer to the core?  perhaps, the proximity of the protons by gravitational.......  aha  LOL  oops

we're talking about a teaspoon.  ok. hydrogen. simple.  maybe deuterium maybe more hydrogen from free neutron excess.  and then the hydrogen wont stick together in a liquid or solid either it will become vapor and that part might be pretty expansive.  it would, however, release gamma rays and antineutrinos.  some of those gamma rays may interact with neutrons and protons or knock off electrons.  this may just become a plasma.  gamma rays would be quite a pop of light. i dont know how many neutronium neutrons would be in a teaspoon? a mole? more than a mole?  avogadro's 10^28 little gamma rays would be a pop of light.  i'd think with these characteristics it might be an 'explosive' reexpansion.  i think the result would be diffuse. (even if stationary).

i suppose by sheer proximity that one neutron turning into a proton could be close enough to stick to the neighboring neutron by fringe-gluon-overlap strong force and then that neutron not decay because its not free anymore.  i could see perhaps some sections of volume doing this without being blown apart by the escaping electrons, and forming a few light nucleii elements, not all nice stable ones, but whatever ones happened to happen.  it depends i think on the speed of the reactions and the speed of separations and the energy released, because gamma rays can kick them around too and make the overlapping fringe of gluons outside a quark triplet too far away for protons and protons or neutrons to stick together by 'strong force'.  (here, strong force is described as a leftover fringe surrounding three quarks and their gluons, the gluons being W and Z particles of varying valence where applicable.  my understanding (from Michio Kaku i think, Hyperspace i think says this) that the weak force particle field extends beyond the quark triplet and the external fringe is how the strong field works, thus combining the two forces's effect, and this apparently is the Yang-Mills theory and the manner by which they just append the data on that to the surrounding metric tensor matrix columns like kalusa-klein theory makes it an essentially one-force addition that is used to build up the mathematics of superstring theory.)

well, i know the names of some of this stuff but i dont know the math.. yet.  ideal Fermi gas is mentioned in Zel'dovich (Stars and Relativity) as degenerate neutron gas, but mostly just referred to by name, i dont have a source on that specifically to show you.

what a fun question.

enjoy :)

jerry

  Ouch....alright....I'll be...okay.

I am so glad I'm going back to school this summer, because I have no idea what the you just said....

I had my own opinion here, but I took it out in favor of a quote from my astronomy book. I think it's much clearer than anything I could say.

In summary, keep your neutron chunks to yourself! I don't want swiss-earth!

"A neutron star is a star of a little over 1 solar mass compressed to a radius of about 10 km. Its density is so high that the matter is stable only as a fluid of neutrons. Theory predicts that such an object would spin a number of times a second, be nearly as hot at its surface as the inside of the sun, and have a magnetic field a trillion times stronger than Earth's. Two questions should occur to us immediately.

The Neutron was discovered in the laboratory in 1932, and its properties suggested something fantastic. Neutrons spin in much the way that electrons do, which means that neutrons must obey the Pauli exclusion principle. (http://hyperphysics.phy-astr.gsu.edu/Hbase/pauli.html) In that case, if neutrons are packed together tightly enough, they can become degenerate just as electrons do. "

Moving on to the point

The core collapses even more than a whitedwarfs, resulting in the breaking down of atomic nuclei by gamma rays. Nearly at the same moment the increasing density forces the released protons to combine with electrons and become neutrons. Then it all becomes a ball of neutrons.

Here's the part I mentioned earlier, "On Earth, Aa sugar-cube-sized lump of this material would weigh 100 million tons. This is roughly the density of the atomic nucleus, and we can think of a neutron star as matter with all of the empty space squeezed out of it."

Now the question is if we somehow seperated it, would the empty space return?

I don't think so, because the equation of gravity shows that it becomes stronger at closer distances, and the same goes for the other three forces. It would take even greater force to break it apart. Now granted, the magnetic forces that keep protons and electrons apart is stronger than gravity, especially at these distances, but we have to remember. The neutron star has already combined all of the protons with the electrons... There is no more charge to push them apart, only the nuclear forces binding the neutrons together, and the gravity pulling ever more material in.

An interesting point, however gravity depends on mass.  Distance does affect the effects of gravity between two masses, but not the strength of a gravitational field.  The neutrons may be closer together, but if only part of the neutron star is present, there isn't enough mass (thus gravity) to hold the neutrons together.  Remember, there is no charge, as you said to either push or pull the neutrons either.  So unless there is something present in atomic physics that isn't being accounted for (like whatever the quarkstar was talking about ), the neutrons would just fly apart, as something other than the original material. 

A really interesting point, though. 

Hehe, now look what you've started Lynxcat!

I don't have a degree in particle physics or anything, I just read a lot of stuff and try my best to assimilate it using (mostly!) logic. And I still stand by my last statement (although I did, of course, simply things a tremendous amount!). Your teaspoonful of neutronium would expand into (mostly) hydrogen.

Quarkstars' last reply attempts to describe how it might expand back. It may not be an instant expansion. It may be an explosive expansion. There might be a flash of light when it happens. But he seems to agree that you would end up with mostly hydrogen (as some kind of vapour).

Lawngazer says a sugar-cube sized lump (which could be a teaspoonful) would weigh 100 million tons. He talks about it not breaking apart because the equation of gravity may not let it.

Turner refutes this, pointing out that it is all still dependent on the mass, which is, in total not enough to hold it together.

So we are back to having it expand (in some manner) into something which is mostly hydrogen.

This is why I love cosmology!

 

What will happen next?  Will the (mostly) hydrogen expand further?  Will the box break?  Will Batman escape in time before it all happens--or will he be neutron soup?  Tune in next week to find out--Same bat-time....same bat-channel!

Oh man dude!!! I totally don't understand this stuff. Let me see if I got any of this right.....    Ok, in a neutron star all the protons and electrons recombined to become neutrons( with a few leftover electrons).

So a neutron star is basicly a big ball of neutorns compressed together with no space between them.

So if you could take a teaspoon sized piece you would have a 100 million tons of neutrons packed into a teaspoon sized lump of matter.

So once in the "lab" your 100 million tons of neutrons would expand out to 100 million tons of hydrogen at normal dencity?? ( I wonder how much space that would take ?)  Why wouldn't it just stay as neutrons, like a 100 million ton cloud of neutrons or something?    I thought a neutron star was the collapsed iron core of the star. So why would they turn into hydrogen? Why not maybe back into iron?

Firstly, please remember that I an no expert in these matters, but this is how I understand the situation (anyone with more knowledge in this area please feel free to correct me here!).

The iron question: Well, most stars spend their life fusing hydrogen into helium, until all fusable material is exhausted at which time they swell into red giants. But heavier mass stars start fusing heavier elements in their cores, until they get iron which is the last possible fusable source. When fusion ceases gravity causes the core to implode, causing a supernova and a neutron star (or black hole) to be left behind. At this point there is no iron, only neutronium (which has had its atomic structure destroyed and thus has no "memory" of what it used to be).

Now, in your lab, the 100 million tons of neutronium doesn't have the mass to stay stable and would now be free neutrons.

While neutrons can be stable when bound inside nuclei, free neutrons are unstable and decay with a half-life of just under 15 minutes. Particles inside the nucleus are typically resonances between neutrons and protons, which transform into one another by the emission and absorption of pions. The only possible decay mode is into a proton, an electron, and an electron antineutrino, the proton and electron forming a hydrogen atom.

Just don't ask me about the electron antineutrino!

Hrmm... I have to disagree with that assumption (That it would expand back into hydrogen...)

 

The atomic equation for a atom of hydrogen is 1 proton, and 1 electron... There are zero neutrons in a normal atom of hydrogen... Also the Neutrons are held together by gluons at this point, a neutron star acts as a gigantic Nucleus... So the nuclear forces are already at work..

I don't believe the neutrons would change back into protons and electrons... Though this is all hypothetical...

So, if the neutrons did expand into protons and electrons then it might actually once again become hydrogen, though at this point in a stars life most of it's hydrogen is already gone... Either ejected out by the nova/super nova or released as planetary nebula (Though in this case that's very improbable since Planetary nebula form from medium-smaller mass stars and neutron stars form from larger massed stars.)

Well... I did a little digging..

A neutron is made up of two down-quarks, one up-quark.

A proton is made up of two up quarks and one down quark.

An electron is not made up of quarks either, as far as quatum physics goes both quarks and electrons are fundamental particals and thus have no size at all...

http://www.physlink.com/Education/AskExperts/ae560.cfm

 

So, I think I'm gonna stand by my original post... I don't think the neutrons would become a proton and an electron pair...*hydrogen*

A neutron star may well act as a giant nucleus, but we aren't in a neutron star anymore. We have isolated a spoonful of neutronium in a laboratory! So maybe there are no nuclear forces already at work, as the neutrons aren't all pressed together anymore?

These are my sources:

http://curious.astro.cornell.edu/stars.php

http://cassfos02.ucsd.edu/public/tutorial/SN.html

http://www.answers.com/topic/neutronium 

http://www.astro.umd.edu/~miller/nstar.html

Unfortunately, real scientists don't seem to want to answer lynxcats question directly....

http://en.wikipedia.org/wiki/Free_neutron