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Fraser
2004-Sep-09, 05:18 PM
SUMMARY: Scientists have theorized that the inside of a neutron star - the remnant from a star that has collapsed under its own gravity - is a special place where the laws of physics begin to break down; atoms are squeezed so tightly by gravity that all protons and electrons are crushed into neutrons which swirl around like a liquid, but without friction (called a superfluid). This theory has gotten some confirmation according to new research from NASA which observed neutron star EXO 0748-676, located 30,000 light years away. Using various instruments, NASA scientists determined that it's approximately 11.5 km (7 miles) in diameter, and contains 1.75 solar masses. With this much mass packed into a small area, the observations match the theory that neutron stars exist in this superfluidic state, but without being crushed further.

What do you think about this story? Post your comments below.

antoniseb
2004-Sep-09, 05:37 PM
an ultra-dense object containing the strangest and rarest matter in the Universe

That's a bold statement! In terms of rarity, I'd guess that there is less Bose-Einstein Condensate in the universe than neutron super-fluid.

All that aside, I like these stories about narrowing down the limits of uncertainty about these things. Great story.

John L
2004-Sep-09, 06:52 PM
And I disagree with the assertion that this is a place where the laws of physics break down. It may be a place where our full understanding is incomplete, but the universe by definition follows the laws of physics. We study objects in the extremes to understand the full extent of those laws.

StarLab
2004-Sep-09, 07:38 PM
I agree with John. The laws of physics do not break down. As a matter of fact, this occurence could be natural by the laws of physics, at such great densities.
By the way, how in the world is it possible that an e- could be "crushed" into a neutron?

Fraser
2004-Sep-09, 07:43 PM
Okay, I poorly chose my words. ;-)

StarLab
2004-Sep-09, 07:44 PM
No, not that, Fraser...I'm wondering how an electron can be turned in a neutron...so, how does that happen?

lswinford
2004-Sep-09, 07:52 PM
Laws usually have limits, exceptions, exclusions, and counter-balancing rules. A law concerning gravity does not fully explain, define, or constrain airplane flight. Simple rules apply to simple situations while the complex and extraordinary need something more complex. I may not be a whiz at physics, but I've seen the history of physicists. Earth-based metaphors and similies work great--on earth. Perhaps we must remember that we are interpreting, in this case, a phenomenon at a distance of 30,000 ly, a little early in the investigation to be challenging our laws before we are sure we've got the whole legal code figured out. :)

(Or, as so amusingly told in a video tale of time travel, paraphrased here "You're just not thinking nth dimensionally.")

antoniseb
2004-Sep-09, 08:02 PM
Originally posted by StarLab@Sep 9 2004, 07:44 PM
I'm wondering how an electron can be turned in a neutron...so, how does that happen?
Actually, what the article said was:

that all protons and electrons are crushed into neutrons

On a practical basis, this is as good a way to describe it as there is. Protons combine with electrons to form neutrons, which take up less space than the proton and electron together [there are other things going on with neutrinos and such, but this explains it well enough].

John L
2004-Sep-09, 08:18 PM
Starlab,

It is a weak nuclear force interaction. Normally one form of radiactive decay involves a neutron decaying into a proton inside the nucleus and ejecting an electron and a neutrino. In the high gravity and densities in the birth of a neutron star, the process is reversed to the point that nearly every proton and electron combine to create a star made of almost nothing but neutrons - hence the name Neutron Star.

StarLab
2004-Sep-10, 03:11 AM
I hope I'm not sounding too pushy, but what's the cusp at which the process begins the reverse? What value does the high gravity and density have to have in order to perform this 'reverse reaction?'

om@umr.edu
2004-Sep-10, 01:17 PM
Originally posted by antoniseb@Sep 9 2004, 08:02 PM
Actually, what the article said was:

that all protons and electrons are crushed into neutrons


The process we observe is:

[1.] neutron -> electron + proton + anti-neutrino

The reverse process is obviously:

[2.] electron + proton + anti-neutrino -> neutron

The reverse process is obviously not:

[3.] electron + proton -> neutron

That would be "Protons and electrons crushed into neutrons".

Maybe there is new physics here.

With kind regards,

Oliver
http://www.umr.edu/~om

mark mclellan
2004-Sep-24, 09:13 AM
Like the idea of superfluids being the densest and most compacted form of matter, almost any solid substance we can find or create can be crushed or shattered if put under enough pressure, whereas a liquid cant be crushed ,shattered of broken !!!! makes sense to me ;) :D :lol: B)

downunder
2004-Sep-27, 05:02 AM
Neutron stars are only found in a very limited range of masses from about 1.4 to 3 times the mass of the sun. Less than 1.4 and there's not enough gravity to cause the collapse to neutrons and more than 3 there's too much gravity and it forms an event horizon...it becomes a black hole.

But there seem to be some evidence that, at least in the core, even the neutrons can be squeezed so tight that they break down into a superfluid of quarks. These free quarks take up less room than neutrons so the density rises (at least at the core) and the star has a smaller diameter than would be expected from a pure neutron star. This raises its surface gravity making it even closer to becoming a black hole so possibly the mass range is considerably less than 1.4 to 3.

How much a particular volume of neutrons collapses to when it becomes free quarks I have no idea but to me it's interesting to wonder if it's possible for a quark star to become small enough to actually form an event horizon without a final collapse to a singularity. From the little I understand it'll have something to do with the degeneracy pressure of free quarks compared to neutrons.

GOURDHEAD
2004-Sep-27, 12:47 PM
How much a particular volume of neutrons collapses to when it becomes free quarks I have no idea but to me it's interesting to wonder if it's possible for a quark star to become small enough to actually form an event horizon without a final collapse to a singularity.

Angular momentum must play an interesting role in the terminal shape of such neutron stars. The centrifugal force near what passes for its equator must create an enormous bulge and the poles must be quite flattened. Are toroid shapes likely?

wstevenbrown
2004-Sep-27, 02:01 PM
Toroids are only a likely configuration for infalling matter, not the neutron star itself. The gravity is so extreme that oblateness is less than 2%, i.e., almost no matter how fast the rotation, the object appears nearly spherical. Most astronomers realize that our understanding of angular momentum transfer is very incomplete, but it is thought to be linked to the coupling of the object's magnetic field to ionized infalling matter. With a very limited statistical universe, we think that naked neutron stars retain much of their angular momentum, whereas "feeding" ones are slowing their rotation. Ask ten astrophysicists, get ten opinions. For a fair treatment, see Kahler, Extreme Stars.

On weak interaction, we see one process daily, as neutrons are not stable. Unbound neutrons decay with a half-life of around 918 sec, in the familiar neutron= proton + electron + antineutrino (electron type). The reverse process is seen locally (almost exclusively) as K-capture: the K-shell electron's probability cloud does not exclude the nucleus, so that while the electron is in critical proximity to a proton, a neutrino happens by, and the three of them merge to form the neutron. The serial probability of these two events happening almost simultaneously is awfully hard to calculate. In any event, it is very rare, but the observable result is that the atom decreases its atomic number by one, with virtually no change in atomic weight. There are those who think that the neutrino involved does not enter the system from outside, but is a virtual particle created by some presently unclear interaction between electron and nucleus. This would violate spin conservation, but hey, there are other processes that do so as well. Inside the horrendous gravity well of a collapsing star, the increasing pressure and temperature increase the probability of the reaction, and positive feedback accelelerates it to runaway speed. Query: did the availability,or the interaction rate of neutrinos generally, suddenly change to accommodate this process? How convenient.

My own pet peeve with this model is "magnetars"-- I just don't see the puny magnetic moments of the neutrons adding up to anything like that, even if politicians were doing the adding. I suspect that the dying star's wind, over the long term, depletes one charge more than another and, when the neutron star forms, the charge excess is preserved (and rotating very fast). Beats counting sheep. :o S.