So the star is losing energy.
Pressure drops, so gravity begins to contract the star.
Pauli Exclusion Principle A rule from quantum mechanics that limits the amount of stuff which can occupy a given space. When densities of matter approach these limits, it is called 'degenerate'. The ideal gas law no longer applies. For degenerate matter, the pressure depends only on density, and not on temperature. Heisenberg Uncertainty Principle States that one cannot simultaneously know exactly where a particle is and also how fast it is moving.