What is electron degeneracy pressure that stops red giants collapsing once they are the size of Earth?

Question: What is electron degeneracy pressure that stops red giants collapsing once they are the size of Earth?
- Keywords:
  electron,
  pressure,
  red giant
Asked by eigenvector to Arttu, Ceri, James_M, Monica, Philip on 19 Jun 2011.
- Arttu Rajantie answered on 19 Jun 2011:
  
  The Pauli exclusion principle states that only one electron can be in each quantum state. If you try to pack a large number of electrons in a small volume, the available quantum states run out. It becomes harder and harder to decrease the volume, so it is as if there was a very high pressure. This is known as the degeneracy pressure. This happens to the electrons when a star collapses, and if the star is not too massive the degeneracy pressure is able to stop the collapse.

eigenvector commented on 19 Jun 2011:

Thanks Arttu! I’ll put this in my Physics A-level paper on Tuesday if a star question comes up!

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Question: What is electron degeneracy pressure that stops red giants collapsing once they are the size of Earth?