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View Full Version : Neutron Stars, Rigid or Plastic?



BigDon
2008-Oct-29, 09:24 PM
If one could bisect a neutron star would the two halves each assume a spherical shape?

If so, would it be gradual or instantaneous?

cjameshuff
2008-Oct-29, 10:20 PM
If one could bisect a neutron star would the two halves each assume a spherical shape?

If so, would it be gradual or instantaneous?

Yes, and quickly...but probably very messily. I've wondered similar things about (enormously unlikely) scenarios such as two neutron stars making a high speed pass within their Roche limits, and thus scattering former neutron star matter all over the place while losing a great deal of mass. Such material is almost certainly not stable outside of the pressures in a neutron star, so I think what you'd end up with would probably be best described as a pair of very odd white dwarfs.

Romanus
2008-Oct-30, 03:05 AM
Ignoring the energy required to split a neutron star, doing so would halve the mass--and hence, gravitational compression--of each half, probably well below the threshold needed to maintain neutron degeneracy. The bottom line: BOOM!

alainprice
2008-Oct-30, 07:48 PM
Wasn't there some talk about neutron stars undergoing 'quakes' as a means for the spin rates to drastically and quickly change.

Wouldn't this imply that the neutron star has some stability(or stacking) within it that limits the 'plasticity' you are referring to?

trinitree88
2008-Oct-31, 12:01 AM
The viscosity of a neutron star is related to it's Reynold number as in :http://www.journals.uchicago.edu/doi/abs/10.1086/505422. The nucleons,(it's not all neutrons, but a mix of neutrons and protons) become distorted into bean shapes, so your traditional modes of close packing for spheres have to be modified ,too. This lends itself to more axisymmetric flows, with the star able to flex it's star quakes with a radial symmetry. I believe one of the other threads indicated that the height of the ridges was ~ the width of a nucleon...it's still smooth.
Free neutrons are affected strongly by magnetic fields of the order of 1011 to 1013 Gauss, having their half-lives drop precipitously...and this is the range of field strenghts of neutron stars. Whether this plays into the polar emissions of neutron stars is in dispute as they expect less effect for bound ones.


Reynolds number, see:http://en.wikipedia.org/wiki/Reynolds_number