The origin of elements
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The origin of elements began with the Big Bang, which formed the lightest elements like hydrogen, helium, and lithium through nuclear fusion in the early hot dense universe. As the universe expanded and cooled, the first stars and galaxies formed, allowing nuclear fusion to produce heavier elements up to iron inside stars. When massive stars collapsed in supernova explosions, even heavier elements were formed through further fusion and neutron capture processes. This cycling of matter between generations of stars through nuclear reactions is how all the chemical elements from carbon to uranium came to exist in the present universe.
The origin of elements
- 1. THE ORIGIN OF ELEMENTS The chapter demonstrates the hitherto known data about the origin of the elements. In this summary will be exposed the most important points of this journey through time. The origin of the universe gives us an answer to the question of how the elements were formed and about the abundance of them in it. According to the big bang theory, all matter in the universe was contained in a primitive nucleus, it is assumed that this nucleus exploded and distributed matter and radiation evenly through space. The universe in initial conditions had matter formed by elementary particles. A second later the universe had a temperature of approximately 10.10 K and was a sea of neutrons, protons, electrons, positrons, photons, and the electron-, muon-, and tau-neutrinos and their antineutrinos, ie hot plasma. In a second, after a period of extensive particle - antiparticle annihilations, the electromagnetic photons are formed. Then the strong nuclear forces caused a large amount of neutrons and protons that combine to give nuclei of Deuterium (n + p) and Helium (2n + 2p). Also the isotopes of helium an lithium were formed, This process is known as big bang nucleosynthesis. The temperature was so high that there were no atoms. As a consequence of the expansion the temperature was decreasing and when 109 ºK was reached nuclear reactions took place in the plasma. Started the weak decoupling where positive particles can capture electrons and form atoms and the novelty is that these reactions are not affected by the electromagnetic radiation that is the atoms can interact with each other independently of the radiation. This interaction leads to the formation of different atoms, which begin to condense and form the nucleus of stars and the radiation expands with the universe. With the presence of gravity, the synthesis of nuclei of chemical elements did not stop. The existence of gravitational attraction led to the formation of zones in space with a large concentration of matter. This process initiated the formation of galaxies and stars which made possible the formation of new chemical elements. The process of formation of matter had a new heating and increase of density which was enough to produce new nuclear reactions. There are some Reaction Cycles during the Synthesis of Heavy Nuclei. First, hydrogen burning where hydrogen is converted to helium, this cycle is called proton- proton. Second, Helium Burning: most of the hydrogen is burned. Helium burning is done, triple-alpha process, fuse to form a carbon nucleus. As soon as carbon is present, the alpha process begins where the formation of neon, oxygen and silicon takes place. Third, Burning of Heavier Elements: If the star is massive (> 8 Solar masses), another set of nuclear fusion reactions begins. These include the burning of carbon, neon, oxygen and silicon that lead to the formation of heavier elements and finally iron. And finally, Production of Heavier Elements Than Iron: After the production of iron, the star collapses under its own gravity to a neutron star or a black hole.