EDWARD'S LECTURE NOTES:
More notes at http://tanguay.info/learntracker
C O U R S E
Formation of the Universe, Solar System, Earth and Life
Henning Haack, University of Copenhagen
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C O U R S E L E C T U R E Nuclear Synthesis: The Origins of Elements in Our Solar System Notes taken on November 22, 2014 by Edward Tanguay |
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nuclear synthesis models come from three separate lines of evidence
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1. composition of our solar system
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the elemental abundances we have in the solar system
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the most important of the three type of evidence
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the atomic structure of atoms
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nucleus
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protons
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neutrons
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electrons
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an element's character is defined by the number of protons in the nucleus
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the number of protons is matched by the number of electrons
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neutrons add mass but do not determine properties
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can vary and gives us a number of set isotopes
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Beryllium example
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four protons, are set in number
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five neutrons, can vary in number
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periodic table
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gives no indication of how often they occur in the universe
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hydrogen and helium make up about 99% of the elements that occur in the universe
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least abundant is uranium
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the nucleus synthetic models have to explain this relative abundance
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how do we know this abundance
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1. meteorites
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chondrites
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the most primitive meteorite
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used to represent the bulk composition of the Solar System
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not so representative for noble gases (helium, neon, argon, krypton, xenon, and radioactive radon) and some volatile elements
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how were the elements formed
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Big-Bang nucleosynthesis
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1967 Nobel Prize in physics
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Stellar nucleosynthesis
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became the standard model which we use today
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1983 Nobel Prize in physics
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3 categories of nucleic production
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1. Big Bang products: Hydrogen, Helium, minor Lithium, Boron, and Beryllium
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all formed in the Big Bang
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created in the instant that the universe formed
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in the first instant you would only have protons and neutrons which begin to combine
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mainly hydrogen and helium
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but the Big Bang theory suggested that all the elements were form this way
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it turns out that there is a fundamental barrier that exists at lithium and Baryllium
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e.g. as you add another proton to Lithium, you come down to Helium again, which is where Stellar explanation accounts for the elements heavier than lithium
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2. Stellar fusion products
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Lithium, Iron, Cobal, Nickel
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everything up to iron-56 combines in fusion reactions
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fusion cannot continue beyond iron-56 because you get lower binding forces after that
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3. products of P, S, and R-nucleosynthesis related to stars and supernovae
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2. experiments on nuclear reactions under set conditions in the laboratory
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3. theoretical constraints on possible sites or environments for nuclear synthetic reactions which are imagined within the laboratory