Fang Lizhi
About the same time, Fang Lizhi, Qu Qinyue, Wang Zhenru and others proposed a theory that abnormal neutron stars, in which neutrons are in a state that their effective mass become zero or nearly zero, are a form of stars during their final period. They studied the stability of these stars, and suggested their maximum mass is approximately 4 solar masses, about twice the Tolman–Oppenheimer–Volkoff limit. Their results demonstrated that meta-stable compact stars can exist.