Known as the densest visible object in the universe,neutron stars have many mysterious properties to be understood.From the external magnetic field through the surface and crust to the core of neu-tron stars,there are many fundamental questions to be addressed[2,3].Thanks to the recent advances espe-cially in radio,X-ray and gravitational wave observations of both isolated neutron stars and their mergers,much progresses have been made in recent years in understand-ing the maximum mass,radius and tidal deformation of neutron stars.These global observables provided some of the much needed constraints on various theories about the equation of state,internal structure and composition of neutron stars.However,because of the scarcity of data available especially those from the un-distorted messen-gers directly from the interior of neutron stars and the model dependence of their interpretations,many myster-ies associated with neutron stars remain to be resolved.In fact,to understand the nature of neutron stars and dense neutron-rich matter has been a long-standing and shared goal of both astrophysics and nuclear physics communi-ties[4,5].