Density, velocity, and pressure at t = 5 × 10⁴ yr with ISM density n_H = 0.1 cm⁻³ and hard‐sphere interior boundary condition. The arrow in the top panel points out a density enhancement, a remnant of the initial conditions; the arrow in the bottom panel points out a secondary shock. The Sedov‐Taylor similarity solution at this time is given with dotted lines.