ocr: LIFESPAN OF THE SUN When the hydrogen resources have been used up, fusion energy will run out of fuel. As the fusion energy will no longer inflate the Sun, gravity will take over and cause the core of the Sun to compress and heat up again. The fusion reaction having transtormed the hydrogen in the Sun's core to helium, the intense pressure will then initiate nuclear reactions of helium. Three helium atoms are there combined into one carbon atom, increasing the intensity of the reaction. As a consequence, the Sun will expand and becomes a red giant. It will become SO huge that its halo will rea ...
