The limit of mass for gravitational collapse and nuclear forces at short distance

On the basis of the current knowledge about the size of the neutron, the nucleon-nucleon interaction, and the limit on the ratioGm/c²R<4/9 imposed by General Relativity, we find an upper limit of about 2M, for stars of uniform density in the neutron phase. The importance of an accurate determination of the neutron radius for neutron stars studies is pointed out.