Kippenhahn diagrams of stars with M_ZAMS = 240 M_⊙ with metallicity Z = 10⁻¹¹ (left), Z = 0.001 (center), and Z = 0.014 (right). The black line indicates the total mass of the star. Blue and green lines show the He and CO cores, respectively. Burning zones are indicated in blue, green, and pink for H, He, and C, while the purple hash indicates the convective zones (CZ). The final He core is indicated on each panel. The red square indicates when X_H^S< 0.3 in mass fraction.