Degenerate Matter

Degenerate matter is a bizarre form of exotic matter created in the cores of massive stars, where atoms or even subatomic particles are packed so closely that the primary source of pressure is no longer thermal but quantum - dictated by limitations set by the Pauli exclusion principle, which asserts that no two particles can occupy the same quantum state. It is also useful in some circumstances to treat conduction electrons in metals as degenerate matter, because of their high density. Degenerate matter, specifically metallic hydrogen, has been created in a laboratory before, using pressures over a million atmospheres (>100 GPa)
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Degenerate matter is unique in that its pressure is only partially dictated by temperature, and pressure would in fact remain even if the temperature of the matter were decreased to absolute zero. This is quite different than the ideal gases we learn about in physics class, where temperature and pressure/volume are closely related.

-K A Solaman