The maximum mass of a neutron star: a didactic approach

Abstract In spite of being a very interesting topic to be discussed in the introductory courses of Astronomy, neutron stars are often presented as a kind of astronomical “anomaly”, and their physics and structure ignored. It is not uncommon to find misleading references to the “Chandrasekhar's mass” linked to them, leading to considerable confusion. We use in this work the simplest form of hydrostatic equilibrium and an elementary discussion of nuclear forces to show 1) that the masses of neutron stars, where matter is found in an extreme regime, are unrelated to Chandrasekhar's mass; 2) that an elementary analysis of stellar equilibrium allows and inference of the solutions as determined by repulsive nuclear forces and 3) that the values of the maximum masses so obtained are in agreement with the most recent measurements of actual neutron stars having > 2 M ⊙ (the latter clearly impossible for the Chandrasekhar's mass).