(a) The Equation of State (EoS) of neutron matter: energy density E/N as a function of neutron density n showing different extrapolations towards neutron-star density. (b) Neutron-star mass versus radius plots solved using the TOV equations with the three different EoS from BSk-19, 20, and 21 (3a) as input [61]. The discovery of the two-solar-mass neutron star in the binary pulsar J1614-2230 [65, 66] rules out the EoS of BSk19, as do J0348+0432 [67] and J0740+6620 [68].