Stars with mass 8 to 25 times Sun mass start with hydrogen and first make helium, then carbon and oxygen, then heavier nuclei, such as silicon, magnesium, and iron. Such massive stars can fuse nuclei to make elements up to iron, which requires temperature 10^12 K. Such stars have turbulent hydrogen, helium, carbon, oxygen, silicon, magnesium, and iron layers, from surface to core, respectively. Star diameter is more than four million kilometers. Iron cannot fuse to anything else, so core becomes cooler and has less pressure. At critical pressure, gravitation collapses iron nuclei in one second to make neutron star. Gravitation continues to pull matter inward, and nuclei bounce off neutron star turbulently at supersonic speed, making shock waves. Nuclei stream inward between shock-wave sides. Neutrinos heat shock-wave gas, which keeps expanding. Shock waves explode star {Type 1b supernova} {Type 1c supernova} {Type 2 supernova} {supernova 2}. Asymmetrical explosion pushes neutron star to speeds up to 1000 km/s. Explosion makes high temperature and pressure and can make elements higher than iron. Perhaps, higher-element making involves antineutrinos. Higher-element making uses energy rather than making energy, absorbs heat, and cools core. Expansion weakens, and gravitational collapse takes several minutes.
Physical Sciences>Astronomy>Star>Kinds
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Date Modified: 2022.0224