Can we decipher the composition of the core of a neutron star?

General relativity guarantees a unique one-to-one correspondence between static observables of neutron stars (NSs) accessible by multimessenger astronomy, such as mass-radius or tidal deformability, and the equation state (EoS) beta equilibrated matter. It is well known that these properties are not enough to discern conventional NSs from hybrid stars. However, if one assumes hadrons present in star core only neutrons protons, lepton fraction expected be determined unequivocally condition chemical equilibrium. Using simple analytical method based on polynomial expansion EoS, we show multiple solutions possible beta-equilibrium equation, leading characteristic indetermination composition interiors NSs, even purely nucleonic hypothesis. We further additional empirical information symmetric matter at high densities very efficient pin down composition, uncertainties measurements accounted for. conclude constraints symmetry energy only, can make meaningful impact decipher core. Our results give lower limit uncertainty NS obtained with astrophysical terrestrial experiments.