Degeneracy Pressure: a type of pressure unrelated to an object’s temperature, which rises when electrons or neutrons are packed so tightly that the exclusion and uncertainty principles come into play.
According to the text book, the basic idea of degeneracy pressure is that the laws of quantum mechanics prevent subatomic particles from getting too close together. To simplify the degeneracy pressure, the text uses an auditorium analogy. The author(s) liken degeneracy pressure to an auditorium in which a number of chairs are spread evenly and people are always moving between the chairs. However, like in protostars with masses below 0.08Msun, in an auditorium with fewer chairs than people, the people can’t all squeeze into a smaller section of the auditorium. This resistance to squeezing is the the origin of degeneracy pressure.
Degeneracy is the cause of brown dwarfs. Because degeneracy pressure halts the contraction of a protostar with a mass less than 0.08Msun before the release of fusion energy can balance the energy radiated from the protostar’s surface, the result is a “failed star” that slowly radiates away it’s internal thermal energy, gradually cooling with time. This is called a brown dwarf. They fit into a “fuzzy gap” that is a cross between a planet and a star.
Also, neutron stars support themselves through neutron degeneracy pressure. Neutron degeneracy pressure comes into play only at much higher densities, because neutrons have much greater mass than electrons. Neutron degeneracy pressure begins to fail when the speed of the neutrons approaches the speed of light. At that point, gravity can make an object shrink further and nothing can stop the collapse of an object once its’ gravity overcomes neutron degeneracy pressure. This causes a black hole to form.