For an independent study course at my high school, I am researching the formation of the elements, both light and heavy. I have some basic understanding of how this is done, and I have also found some technical information that at this time I don't understand. Can you point me to some good articles on the topic, or perhaps cover some more advanced materials yourself? The lightest elements (hydrogen, helium, deuterium, lithium) were produced in the Big Bang nucleosynthesis. According to the Big Bang theory, the temperatures in the early universe were so high that fusion reactions could take place. This resulted in the formation of light elements: hydrogen, deuterium, helium (two isotopes), lithium and trace amounts of beryllium. Nuclear fusion in stars converts hydrogen into helium in all stars. In stars less massive than the Sun, this is the only reaction that takes place. In stars more massive than the Sun (but less massive than about 8 solar masses), further reactions that convert helium to carbon and oxygen take place in succesive stages of stellar evolution. In the very massive stars, the reaction chain continues to produce elements like silicon upto iron. Elements higher than iron cannot be formed through fusion as one has to supply energy for the reaction to take place. However, we do see elements higher than iron around us. So how did these elements form? The answer is supernovae. In a supernova explosion, neutron capture reactions take place (this is not fusion), leading to the formation of heavy elements. This is the reason why it is said that most of the stuff that we see around us come from stars and supernovae (the heavy elements part). If you go into technical details, then there are two processes of neutron capture called rapid process (r-process) and the slow process (s-process), and these lead to formation of different elements. For more details, refer the following websites: 1. Big Bang nucleosynthesis 2. Fusion in stars like the Sun 3. s-process and r-process This page was last updated June 27, 2015.
 Jagadheep built a new receiver for the Arecibo radio telescope that works between 6 and 8 GHz. He studies 6.7 GHz methanol masers in our Galaxy. These masers occur at sites where massive stars are being born. He got his Ph.D from Cornell in January 2007 and was a postdoctoral fellow at the Max Planck Insitute for Radio Astronomy in Germany. After that, he worked at the Institute for Astronomy at the University of Hawaii as the Submillimeter Postdoctoral Fellow. Jagadheep is currently at the Indian Institute of Space Scence and Technology.
nuclear fusion, process by which nuclear reactions between light elements form heavier elements (up to iron). In cases where the interacting nuclei belong to elements with low atomic numbers (e.g., hydrogen [atomic number 1] or its isotopes deuterium and tritium), substantial amounts of energy are released. The vast energy potential of nuclear fusion was first exploited in thermonuclear weapons, or hydrogen bombs, which were developed in the decade immediately following World War II. For a detailed history of this development, see nuclear weapon. Meanwhile, the potential peaceful applications of nuclear fusion, especially in view of the essentially limitless supply of fusion fuel on Earth, have encouraged an immense effort to harness this process for the production of power. For more detailed information on this effort, see fusion reactor. This article focuses on the physics of the fusion reaction and on the principles of achieving sustained energy-producing fusion reactions. Fusion reactions constitute the fundamental energy source of stars, including the Sun. The evolution of stars can be viewed as a passage through various stages as thermonuclear reactions and nucleosynthesis cause compositional changes over long time spans. Hydrogen (H) “burning” initiates the fusion energy source of stars and leads to the formation of helium (He). Generation of fusion energy for practical use also relies on fusion reactions between the lightest elements that burn to form helium. In fact, the heavy isotopes of hydrogen—deuterium (D) and tritium (T)—react more efficiently with each other, and, when they do undergo fusion, they yield more energy per reaction than do two hydrogen nuclei. (The hydrogen nucleus consists of a single proton. The deuterium nucleus has one proton and one neutron, while tritium has one proton and two neutrons.) Fusion reactions between light elements, like fission reactions that split heavy elements, release energy because of a key feature of nuclear matter called the binding energy, which can be released through fusion or fission. The binding energy of the nucleus is a measure of the efficiency with which its constituent nucleons are bound together. Take, for example, an element with Z protons and N neutrons in its nucleus. The element’s atomic weight A is Z + N, and its atomic number is Z. The binding energy B is the energy associated with the mass difference between the Z protons and N neutrons considered separately and the nucleons bound together (Z + N) in a nucleus of mass M. The formula is B = (Zmp + Nmn − M)c2, where mp and mn are the proton and neutron masses and c is the speed of light. It has been determined experimentally that the binding energy per nucleon is a maximum of about 1.4 10−12 joule at an atomic mass number of approximately 60—that is, approximately the atomic mass number of iron. Accordingly, the fusion of elements lighter than iron or the splitting of heavier ones generally leads to a net release of energy. Fusion reactions are of two basic types: (1) those that preserve the number of protons and neutrons and (2) those that involve a conversion between protons and neutrons. Reactions of the first type are most important for practical fusion energy production, whereas those of the second type are crucial to the initiation of star burning. An arbitrary element is indicated by the notation AZX, where Z is the charge of the nucleus and A is the atomic weight. An important fusion reaction for practical energy generation is that between deuterium and tritium (the D-T fusion reaction). It produces helium (He) and a neutron (n) and is written D + T → He + n. To the left of the arrow (before the reaction) there are two protons and three neutrons. The same is true on the right. Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now The other reaction, that which initiates star burning, involves the fusion of two hydrogen nuclei to form deuterium (the H-H fusion reaction): H + H → D + β + + ν, where β + represents a positron and ν stands for a neutrino. Before the reaction there are two hydrogen nuclei (that is, two protons). Afterward there are one proton and one neutron (bound together as the nucleus of deuterium) plus a positron and a neutrino (produced as a consequence of the conversion of one proton to a neutron). Both of these fusion reactions are exoergic and so yield energy. The German-born physicist Hans Bethe proposed in the 1930s that the H-H fusion reaction could occur with a net release of energy and provide, along with subsequent reactions, the fundamental energy source sustaining the stars. However, practical energy generation requires the D-T reaction for two reasons: first, the rate of reactions between deuterium and tritium is much higher than that between protons; second, the net energy release from the D-T reaction is 40 times greater than that from the H-H reaction. |
What is the process of formation of heavy elements by the fusion of lighter nuclei in the interior of starts Brainly?
zusammenhängende Posts
Urheberrechte © © 2024 frojeostern Inc.
