Neutron Star Mass–Radius Relation (2D)

A neutron star is held up not by Newtonian gas pressure but by degenerate neutron matter fighting the extreme curvature of its own gravity, described by the Tolman–Oppenheimer–Volkoff (TOV) equation. This 2D simulator solves that equation numerically in real time: pick a central density and an equation-of-state stiffness, and a 4th-order Runge–Kutta integrator builds the star's density profile outward from the core to its surface, rendering the resulting mass and radius as a 2D cross-section with its Schwarzschild radius drawn for scale. A live mass–radius curve traces the full family of solutions for the chosen equation of state, showing the turnover that marks the maximum-mass limit — the point beyond which no stable neutron star can exist and the remnant must collapse into a black hole.