The degeneracy pressure of the electrons can stabilize the collapse of a star due to gravity by equating the gravitational inward pressure with the outward electron gas degeneracy pressure. These cold stars called white dwarfs have small radii compared to their original size and this radius decreases as the original mass of the star increases. As the mass of a star increases, the electron energy increases to a point in which their energy has to be treated relativistically. (a) Evaluate the degeneracy pressure for ultra-relativistic electrons (problem 2, above). (b) As the pressure increases, the reaction e − + p → n + ν takes place. The neutrinos (ν) escape as matter is transparent to them, electrons and protons convert to neutrons until we are left with a neutron star. Using your expression for the degeneracy pressure obtained in (a) above, equate the gravitational pressureto the neutron degeneracy pressure (replace the electron’s mass in your degeneracy pressure expression from (a) with the neutron’s mass) and numerically obtain the radius of a neutron star assuming a star with a mass equal to one solar mass. Take the number of nucleons in the star to be N = 1.2 × 1057 .
The degeneracy pressure of the electrons can stabilize the collapse of a star due to gravity by equating the gravitational inward pressure with the outward electron gas degeneracy pressure. These cold stars called white dwarfs have small radii compared to their original size and this radius decreases as the original mass of the star increases. As the mass of a star increases, the electron energy increases to a point in which their energy has to be treated relativistically.
(a) Evaluate the degeneracy pressure for ultra-relativistic electrons (problem 2, above).
(b) As the pressure increases, the reaction e − + p → n + ν takes place. The neutrinos (ν) escape as matter is transparent to them, electrons and protons convert to neutrons until we are left with a neutron star. Using your expression for the degeneracy pressure obtained in (a) above, equate the gravitational pressureto the neutron degeneracy pressure (replace the electron’s mass in your degeneracy pressure expression from (a) with the neutron’s mass) and numerically obtain the radius of a neutron star assuming a star with a mass equal to one solar mass. Take the number of nucleons in the star to be N = 1.2 × 1057 .
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