Exploring the Role of Electron Degeneracy in White Dwarf Stars

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In summary, a white dwarf is held up by electron degeneracy, where all electrons are under immense pressure but cannot fall to the lowest energy state. Despite this, the star is able to emit light due to some particles being excited above the Fermi level and interacting with other particles such as photons. This interaction is caused by the high temperature created by immense pressure. Additionally, it is believed that the degeneracy only occurs in the lower levels of the white dwarf, while electrons can still move on the upper levels and with the atmosphere on the surface.
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Johnahh
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Yesterday i had a thought about when our sun runs out of energy and collapses into a white dwarf, it is my understanding when this happens a white dwarf is held up by electron degeneracy, all the electrons are under immense pressure but cannot fall to the lowest energy state therefore stopping the star from collapse due to gravity.
My question is how can this star still emit light as the electrons cannot change energy levels?
Unless my understanding of degeneracy is wrong and they can in fact change energy levels, if this is the case would anyone care to explain?

thanks
 
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At absolute zero the degeneracy is complete. All the states up to the Fermi level are occupied, and particles are unable to move from one state to another. (Electrons in a white dwarf, neutrons in a neutron star.) But at a finite temperature some of the particles are excited above the Fermi level, leaving vacancies, where some of them interact with other particles, such as photons.
 
  • #3
[QUOTEAt absolute zero the degeneracy is complete. All the states up to the Fermi level are occupied, and particles are unable to move from one state to another. (Electrons in a white dwarf, neutrons in a neutron star.) But at a finite temperature some of the particles are excited above the Fermi level, leaving vacancies, where some of them interact with other particles, such as photons.][/QUOTE]

Is it the immense pressure that is causing this high temperature creating interactions?
 
  • #4
I think the degeneracy only occurs in the lower levels of the white dwarf, whereas on the upper levels and with the atmosphere on the surface electrons can still move.
 

What is a white dwarf?

A white dwarf is a small, dense star that is the end stage of a medium-sized star's life. It is the leftover core of a star after it has run out of fuel and shed its outer layers.

How does degeneracy play a role in white dwarfs?

Degeneracy refers to a phenomenon in which particles, such as electrons, are packed so closely together that they cannot occupy the same energy state. In white dwarfs, degeneracy pressure is what keeps the star from collapsing under its own gravity, as it has no nuclear fusion reactions to counteract the force.

What is the Chandrasekhar limit and how does it relate to white dwarfs?

The Chandrasekhar limit is the maximum mass that a white dwarf can have before it will collapse and explode as a supernova. This limit is approximately 1.4 times the mass of our Sun, and it is due to the increasing degeneracy pressure as the white dwarf's mass increases.

How do white dwarfs cool down?

White dwarfs cool down over time through a process called thermal radiation. As they do not have any nuclear fusion reactions to generate heat, they gradually lose their thermal energy and become dimmer and cooler.

What is the fate of a white dwarf?

The fate of a white dwarf depends on its mass. A white dwarf with a mass less than the Chandrasekhar limit will continue to cool down until it becomes a cold, dark object known as a black dwarf. A white dwarf with a mass greater than the limit will eventually collapse and explode as a type Ia supernova.

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