ocr: EXPLODING STAR When a star with the mass of the Sun or Sun larger has used up the hydrogen required for fusion reactions, it begins to shrink, and thus heats up again. This initiates the fu- sion reactions of helium, and the star begins to expand. It becomes a giant. As helium runs out, the heavier elements ini- tiate their fusion reactions. The largest stars Sun fuse all elements up to iron. As a large star has used up all its energy Pic 1: The Sun compared to a giant. supplies, a supernovo explosion takes Pic dwart. 2: The Sun compared to a white place. The outer parts of the star disperse i ...
