Figure 12-2The Structure of an Old Intermediate-Mass Star Near the end of its life, an intermediate-mass star, like the Sun, travels up the AGB and becomes a red supergiant. (The Sun will eventually be about as large as the diameter of Earth’s orbit.) The star’s inert core, its helium-fusing shell, and its hydrogen-fusing shell are contained within a volume roughly the size of Earth. The inner layers are not shown to scale here.