Neutron and electron degeneracy pressure and their applications to neutron stars and white dwarfs
Nikanova Oleksandra
Low and high mass stars fuse hydrogens into helium
The heat in the core provides hydrostatic equilibrium – the inward pull of gravity in the star and the outward pressure that nuclear reactions create are balanced
Red giant phase (used all the hydrogen at their cores)
Stars that are 5 or more times the sun’s mass fuse elements until their core is made of iron (too heavy, fusion stops, gravity takes over and gravitational collapse begins)
The outer layers of the star collapse and bounce off the iron core at 30 thousand km/sec, which creates shock waves through the star
Supernova explosion (the pressure is so high that the atoms are smashed together, leaving only neutrons)
The remnant left after the explosion is a fast-spinning neutron star .
If a neutron star is too massive, neutron degeneracy pressure fails and the remnant collapses into a black hole
If a neutron star is no more than 3 solar masses, neutron degeneracy pressure stabilizes the remnant and causes the neutron star to slow down its rotation.
What is electron degeneracy pressure? How does it relate to white dwarfs?
Each electron’s state or position can be determined by the 4 quantum numbers (they locate the electron’s shell, subshell, orbital and the direction of the rotation). The Pauli Exclusion principal states that no 2 electrons can occupy the same state, thus cannot have the same 4 quantum numbers.
Low mass stars like our sun fuse elements to the point when their core is composed of oxygen and carbon, which can’t be fused anymore.
Red giant phase as core expands and gets hotter
Planetary nebula (It will continue expelling the material until only a carbon-oxygen core is left behind)
That core is called a white dwarf – very dense because of the Pauli Exclusion principal (once the lowest energy level is full, electrons are forced into higher and higher levels; so densely packed that they can’t squeeze any further; they form a force within the remnant which prevents the white dwarf from collapsing).
Chandrasekhar limit of 1.44 solar masses – a white dwarf accretes material in a binary system and exceeds the limit, it turns type IA supernova
To recap:
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