Unlike a classical ideal gas, whose pressure is proportional to its temperature P = k B N T V , where P is pressure, k B is the Boltzmann constant, N is the number of particles (typically atoms or molecules), T is temperature, and V is the volume, the pressure exerted by degenerate matter depends only weakly on its temperature. In particular, the pressure remains nonzero even at absolute zero temperature. At relatively low densities, the pressure of a fully degenerate gas can be derived by treating the system as an ideal Fermi gas, in this way P = ( 3 π π 2 ) 2 / 3 ℏ ℏ 2 5 m ( N V ) 5 / 3 , where m is the mass of the individual particles making up the gas. At very high densities, where most of the particles are forced into quantum states with relativistic energies, the pressure is given by P = K ( N V ) 4 / 3 , where K is another proportionality constant depending on the properties of the particles making up the gas.