Starting with hydrogen, stars first make helium, then carbon and oxygen, then heavier nuclei, such as silicon, sulfur, and calcium. Heat dissipates, and star stops fusion. Star still has high temperature and turbulence. Helium rises to surface, and heavier nuclei go to core. White-dwarf stars have no hydrogen and are small. White dwarfs orbiting stars with larger diameters but smaller masses can become supernovas {Type 1a supernova} {supernova 1a}. White dwarfs accrete gas from other star, until gas has enough matter to pressure star core to restart nuclear reactions. From carbon and oxygen, chain reactions produce nickel, iron, and cobalt and, after several seconds, explode star.
Physical Sciences>Astronomy>Star>Kinds
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Date Modified: 2022.0224