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Just how spherical is a neutron star?

  1. Dec 12, 2011 #1
    I recently read an article that said that experiments in synchotrons had indicated that an electron was the most spherical object in the universe. It stated that if an electron were the same diameter as the solar system, the variation in its diameter would be less than the thickness of a human hair.

    However, whilst I was thinking about neutron stars in general, and pulsars in particular, it struck me that with the extreme dimensions and conditions involved, 1.3 - 2 times the solar mass compacted into an 20 mile diameter star, spinning at up to 712 revolutions per second, surely, if there even the slightest amount of asymmetry, the forces involved would simply cause it to tear itself asunder.

    Does anyone know if there has been any research in this field and, if there has, how would the symmetry of a millisecond pulsar compare to that of an electron?
  2. jcsd
  3. Dec 12, 2011 #2


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    2 solar masses packed into 20 miles diameter, spinning at 100/sec, would have a diameter at the equator that is almost 1% more than at the poles.
  4. Dec 13, 2011 #3
    In addition, a Neutron Star has "mountains" ≤ 1 inch high.
  5. Dec 13, 2011 #4
    Yes, there is research in this area. In a neutron star the highest mountain is on the order of millimeters. Anything larger than that and energy is radiated in the form of gravitational waves.

    Millisecond pulsars are quite oblate. The limit on their rotational speed is when the spheroid begins to become ovoid, again resulting in gravitational waves.

    Neutron stars have such strong gravity that tearing apart under rotational stress is not really a possibility. The crust is over a billion times stronger than steel and 1km thick. Nevertheless the accumulated twist of the magnetic field grows so great that the crust shears and ruptures, leading to the most energetic events observed in this galaxy.

    I've been told that electrons are point-like. They have no known radius, so I don't know how they could be spherical.
  6. Dec 13, 2011 #5
    Thanks chaps, most enlightening.

    An article about the spherical nature of electrons can be found Here
  7. Dec 13, 2011 #6


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    From the linked article above:

  8. Dec 15, 2011 #7


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    A neutron star is probably very spherical. It is composed of matter with a calculated Young's modulus about 20 orders of magnitude greater than any known material. I recall once reading the equivalent of mount everest on a neutron star would be about a millimeter high.
  9. Dec 24, 2011 #8
    I'm shocked that neutron stars can even have "mountains" greater than a few nanometers.
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