Supernovae are energetic events that occur when massive stars run out of nuclear fuel and collapse. Explosive nucleosynthesis creates heavy elements and temperatures of billions of degrees. Supernovae are responsible for creating elements heavier than iron, while stellar nucleosynthesis creates hydrogen and helium. The Big Bang nucleosynthesis fused hydrogen atoms into helium nuclei, resulting in the current composition of the observable universe.
Explosive nucleosynthesis is the creation of heavy elements that takes place in the heart of a supernova. A supernova is an extremely energetic astronomical event in which a supergiant star runs out of nuclear fuel and collapses under its own gravity. Infalling matter bounces off a superdense nucleus, creating an explosion and a shock front that shoots away from the nucleus at speeds of up to 2000 km/s. A supernova can eclipse its host galaxy and have been observed by astronomers since ancient history.
Stars obtain their energy through the fusion of atomic nuclei, mainly hydrogen and helium. This is called the combustion of hydrogen and helium. In very massive stars, the burning of these elements creates an “ash” of increasingly heavier elements – carbon, neon, silicon, iron and nickel – until eventually the amount of energy needed to fuse the nuclei exceeds the energy it releases. and the nuclear chain reaction is extinguished. What’s left is an iron-nickel core made up of about 1.38 solar masses, which then rapidly collapses into a neutron star or black hole, causing a supernova from the bounce. Another type of supernova, called a type Ia supernova, occurs in less massive stars. A Type Ia supernova occurs when a carbon-oxygen white dwarf star passes the same solar mass threshold of 1.38 and burns up all of its contents within seconds.
In both types of supernova, temperatures on the order of billions of degrees are created at the center, and several solar masses of material are ejected outward at 3% of the speed of light. Although fusing iron and nickel nuclei together is very expensive in terms of energy, a supernova is more than enough to start the necessary reactions. Every element heavier than iron on the periodic table is either created in supernova explosions or is a decay product of those elements.
Supernova nucleosynthesis is just one category of nucleosynthesis. The most typical type of nucleosynthesis is stellar nucleosynthesis, mainly of the hydrogen-helium burning type mentioned earlier. There is also the Big Bang nucleosynthesis, which occurred during the first three minutes of the universe’s existence. During this event, 24% of the initial hydrogen atoms in the cosmos were fused into helium nuclei. Currently, the observable universe is made up of about 74% hydrogen, 24% helium, 1% oxygen and 1% other elements.
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