Silicon-burning nuclear fusion. Animation showing the mechanism of the nuclear fusion reaction between nuclei of silicon and helium. This is the final stage of nuclear fusion for massive stars that have run out of lighter fuels. It is preceded by oxygen-burning nuclear fusion, lasts about one day, and is followed by a supernova explosion as the core of the star collapses. The atomic nuclei consist of protons (red) and neutrons (yellow). The silicon is produced from oxygen-burning nuclear fusion, which is the first reaction shown: two nuclei of oxygen-16 (with 8 protons and 8 neutrons) fuse to form a nucleus of silicon-28 (14 protons, 14 neutron) and a nucleus of helium-4 (an alpha particle; 2 protons, 2 neutrons). This is followed by eight successive additions of helium-4 nuclei, producing more and more massive nuclei: sulphur-32, argon-36, calcium-40, titanium-44, chromium-48, iron-52, nickel-56 and zinc-60. This silicon-burning process created many of the heavier elements found on the Earth and other planets. |