What Prevents Electrons from Expanding Radially in White Dwarfs?

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Discussion Overview

The discussion revolves around the mechanisms that prevent electrons from expanding radially in white dwarfs, focusing on the roles of electron degeneracy pressure and electromagnetic forces. Participants explore theoretical aspects and implications of these forces in the context of stellar structure.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that electron degeneracy pressure is the primary mechanism resisting gravitational collapse in white dwarfs.
  • One participant suggests that electromagnetism plays a crucial role, arguing that if electrons were to migrate outward, it would create a charge imbalance that would generate a restoring force to maintain neutrality.
  • There is a discussion about the possibility of slight variations in local net charge within the white dwarf, which could affect the behavior of electrons differently at various depths.
  • Questions arise regarding whether the restoring force leads to zero electron expansion or allows for some expansion until forces balance, specifically in relation to Fermi pressure.
  • Another participant challenges the influence of local charge variations, asserting that they would not significantly affect electron behavior under the pressure required to support a star's mass.

Areas of Agreement / Disagreement

Participants express differing views on the primary forces at play, with some emphasizing electromagnetism while others focus on electron degeneracy pressure. The discussion remains unresolved regarding the extent and nature of electron expansion in relation to these forces.

Contextual Notes

Participants acknowledge uncertainties regarding the influence of local charge variations and the balance of forces involved in electron behavior within white dwarfs. There are also unresolved questions about the implications of these forces on electron expansion.

MarkL
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From Wikipedia : White dwarfs resist gravitational collapse primarily through electron degeneracy pressure

What prevents electrons from expanding radially through the space between the ions (carbon, say)?
 
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Gravity?
 
No, electromagnetism I think. If electrons were to migrate outwards the inner part would acquire a positive charge and the outer part a negative charge, which would rapidly become a very strong restoring force bringing back neutrality.

It is possible that you might find that there is a slight variation in local net charge with depth as various different effects push or pull slightly differently on different particles. I don't know for certain. You won't get a pure nucleon core withan electron atmosphere, though.
 
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bring back...or expand till
 
Huh?
 
the answer above was: "restoring force bringing back neutrality"
Does this mean,
bring back (to neutrality) = zero electron expansion or prevents electron expansion
or
expand till (neutrality) = electrons expand till force equals fermi pressure = some electron expansion
 
MarkL said:
the answer above was: "restoring force bringing back neutrality"
Does this mean,
bring back (to neutrality) = zero electron expansion or prevents electron expansion
or
expand till (neutrality) = electrons expand till force equals fermi pressure = some electron expansion
As my last paragraph said:
Ibix said:
It is possible that you might find that there is a slight variation in local net charge with depth as various different effects push or pull slightly differently on different particles. I don't know for certain.
I'm not sure what question you are asking that isn't answered by that.
 
Your last paragraph would never influence an electron with enough pressure to support the mass of a star.
Your first paragraph, however, is spot on and intuitive.
And I'm good...thanks for your response.
 

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