the red giant has enough mass, gravity will compress it so tightly that its core gets hotter than ever before, hot enough to start fusing helium nuclei into heavier nuclei, such as carbon (with six protons) and oxygen (with eight protons). The star has revived, but fusing helium nuclei is a more complicated process than fusing protons and generates less energy, so stars at this stage have a much shorter life expectancy. Very large stars will go through several stages of increasingly frenetic expansion and contraction. Carbon and oxygen will fuse to form elements from magnesium to silicon and
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