| Summary: | 碩士 === 淡江大學 === 物理學系 === 85 === In this thesis we first discuss three fundamental aspects of
compact stars: the hydrostatic equilibrium, polytropes and Lane-
Emden equation. The idea of polytropes first originated from the
works of Lord Kelvin. Combining the equation of hydrostatic
equilibrium and polytropes, we obtain the Lane-Emden equation.
White dwarfs are considered as spherical distributed ideal gas
of highly degenerate electrons. In both the non-relativistic
limits and the highly relat-ivistic limits, the white dwarfs are
polytropes. So we can use the Lane-Emden equation. In the highly
relativistic limits we obtain the mass limit of the white
dwarfs, which is 1.4 times the solar mass. This limit is called
the Chandrasekhar limit. By the same consideration, we can
compute the mass limit of the neutron star, which is 5.69 times
the solar mass. For large mass and high density, we must take
into account the effect of the general relativity. According to
the Oppenheimer-Volkoff's ideal neutr- on gas model, the
limiting mass is found to be 0.7 times the solar mass. In
fact, an actual neutron star will have different layers of
structures: the surface ( composing of irons ), the out crust (
composing of the heavy nucl- ei and electrons ), the inner crust
( composing of the neutron-rich nuclei and neutrons ), the
neutron liquid and the core. Up to now the core's struct- ure is
uncertain. For the core we may have several possibilities: the
neutron solid, the hyperon liquid, ( condensation and the quark
matter. In the last chapter we consider the chemical
equilibrium of the neutron star, assumed to be composed almost
entirely of neutrons and little amount of protons and electrons.
The maximum of proton-neutron ratio is 1/8.
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