Neutron stars are made of highly compressed material called degenerate matter, which is so dense it must be described using the laws of quantum mechanics. As a result, NSs should have a unique relationship between mass and radius, determined by an “equation of state” (EoS). An EoS is a thermodynamic description of the entwined properties of, for example, temperature, pressure, and volume. The steam in a pressure cooker can be described by an EoS; so can the interior of a star. For neutron star-like conditions only density matters, which results in a density-dependent EoS, P(rho). But because their material is in an exotic state not found anywhere on Earth, the EoS for neutron stars remains unknown.