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B Do neutron stars have a minimum volume?

  1. Mar 30, 2017 #1
    Do neutron stars have a minimum volume? Anything "in the way" of perhaps baseball sized neutron star? Or would something like that be an impossibility?

    How neat to have one in a laboratory...or not lol
  2. jcsd
  3. Mar 30, 2017 #2


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    You need enough mass to maintain the pressure required for a neutron star. It might be possible to make artificial neutron stars a bit smaller than natural ones, but that still means something like 1 solar mass.
    In terms of size: More massive neutron stars are actually a bit smaller. But if you make them too massive, they collapse to a black hole.

    => all neutron stars have a radius of a few kilometers
  4. Mar 30, 2017 #3
    So much for my neutron baseballs baseball company. :D

    such an interesting phenomenon , I imagine all the cool physicists study such massive bodies. lol But no neutron stars in the "lab".

    Apparently some rotate at as much as 70% of c!! Angular momentum anyone? a few km radius "ball of immense energy" of pretty much every form in extremes lol

    I wonder how fast they dissipate all but their (rest) mass.
    Last edited: Mar 30, 2017
  5. Mar 31, 2017 #4


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    Not that much - smaller than the star that collapsed. Large v, but small r doesn't make a large product vr.

    They slow down in their rotation over time and they get colder. If they don't catch enough mass to convert to a black hole, they will still spin quite rapidly when they are cold.
  6. Mar 31, 2017 #5
    lol with all do respect you are making light of an object 12 km wide of some of the most dense "pile" of matter spinning at the better part of c.

    I appreciate, perhaps in a different way than you that the angular momentum is less in this stage of a star, but in the context of the size of the object.....it could fit "on" earth... I can actually visualize the size of it, I've walked that distance....to think an "extreme" astronomical phenomena could be "familiar" in any way is unusual for me, particularly size.

    curious if we could play with such dense matter that gravity wouldn't be so elusive from a measurement perspective.
  7. Mar 31, 2017 #6


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    Well, compared to everyday objects or planets the angular momentum is huge, of course. Compared to other objects with a similar mass as the neutron star it is not.

    Even if a smaller amount with that density would be stable, you couldn't play with it, everything large enough to be visible would just crush the ground and fall towards the core of Earth.
  8. Apr 3, 2017 #7
    Fast rotation of NS does not strike me as particularly amazing, considering other properties on NS.

    Such as magnetic fields with astounding energy density, more than energy density in a form of "usual matter" around us.

    Just think about that. Antimatter is often thought of as "ultimate energy storage" in terms of density, ~1000 times denser than U235.

    But here, we have just the "boring old" electromagnetic field, in vacuum, tangled up so tightly, it has much, much more energy per unit volume than antimatter (at STP) would!

    Magnetic reconnections on the Sun cause solar flares. This is basically magnetic field jumping into a less energetic configuration.

    Magnetic reconnections on a NS are far, far, *FAR* scarier. They happen in microseconds, they release energy equivalent to many tons of mass, and (since it's *EM* field) they easily convert this energy into EM waves, meaning gamma-rays. The "empty space" filled with magnetic field suddenly turns into a gamma-ray inferno.

    Everyone knows about immense gravity on the surface, but just how immense it is, it's hard to visualize.
    On the surface, a test object would fall one meter in about one millisecond - and attain velocity of several thousand km/s!
    If a material baryonic object (a rock) would fall on NS from infinity, it would heat on impact to the temperature on the order of *trillion kelvins*!
  9. Apr 3, 2017 #8
    It was the magnetism and rotation that got me thinking more about them....the very magnetic ones will have the spin slowed remarkably by interactions, from there the idea all of this in a space 12km wide was just so wow! Second was about the tidal effects of such a tiny tiny object. I wonder what is the most dense energy we've reached ("massive / macroscopic")

    Another neat consideration is the repulsive forces of the particles, the gravity containing it and the balance struck. Particularly for a "cold" or "dead" one.

    Apparently at the LHC they've found possible "(quark &) gluon plasma", to which inserted in the article was a comment from a scientist that said "Besides black holes, there's nothing denser that we're creating." I wonder if that is the same as him saying, quark-gluon plasma is the last step before a black hole.
    Last edited: Apr 3, 2017
  10. Apr 3, 2017 #9
    Coolest experiment ever!
  11. Apr 4, 2017 #10


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    The quark gluon plasma created at the LHC is hotter than the core of neutron stars. It should also have a higher density.

    The cores of neutron stars have a density slightly higher than the nuclei of heavy elements in regular matter.
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