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Nuclear Astrophysics

Nuclear Astrophysics. by Richard Cyburt. Creation of new elements is energy source of stars (and the sun). “We are made of star stuff….” Carl Sagan. The sun shines. 3.85e33 erg/s = 3.85e26 Watts. for at least ~4.5 bio years. The entire sun made of coal would last ~ 4000 years.

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Nuclear Astrophysics

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  1. Nuclear Astrophysics by Richard Cyburt

  2. Creation of new elements is energy source of stars (and the sun) “We are made of star stuff….” Carl Sagan

  3. The sun shines 3.85e33 erg/s = 3.85e26 Watts for at least ~4.5 bio years The entire sun made of coal would last ~ 4000 years

  4. NucleusFactories

  5. Question 3How were the elements from iron to uranium made ? (main question: r-process) Committee for the Physics of the Universe (NRC/NAS) “Connecting Quarks with the Cosmos” – 11 science questions for the new century

  6. Periodic Table of Elements in nature

  7. Elements in nature Made in the Big Bang

  8. Elements in nature Made by fusion in stars…

  9. Elements in nature How are the elements heavier than iron made?

  10. Burning stages of a 25 solar mass star initially present: mostly hydrogen (~70% - from big bang) Hydrogen burning Hydrogen (1p,0n) Helium (2p, 2n) 7Mio yrs Helium burning Helium (2p,2n) Carbon (6p, 6n), Oxygen (8p,8n) 700,000 yrs Carbon(+Ne) burning Carbon (6p,6n) Oxygen (8p,8n) 400 yrs Oxygen burning Oxygen (8p,8n) Silicon (14p,14n) 8 months Silicon burning Silicon (14p,14n) Nickel (28p,28n) 1 day

  11. Average binding energy per nucleon (MeV) For stable nuclei !!!

  12. Window of the Protestant church in Wixhausen, Germany

  13. Precollapse structure of massive star Iron core collapses and triggers supernova explosion

  14. How to make Gold ... and the other heavy elements

  15. Atomic Nucleus Proton Neutron

  16. What is the universe made of? Hydrogen: Helium: Mass number = 1 Mass number = 4 Observed Nuclei in the Universe: 91.0% Iron ? 8.9%

  17. What is the Universe made of?

  18. Iron: Gold: 26 protons + 30 neutrons 79 protons + 118 neutrons Mass number = 56 Mass number = 197

  19. Gold (197Au) 197Au: Au has 79 protons197Au has 197 – 79 = 118 neutrons number of protons Helium number of neutrons Hydrogen

  20. Gold (197Au) 197Au: Au has 79 protons197Au has 197 – 79 = 118 neutrons number of protons Helium number of neutrons Hydrogen

  21. So how is gold made ? Some earlier failed attempts (1590) … by Alchemy: For example: with the “Philosopher’s Stone” Making gold/silver from base metals NSCL (present day) Alchemists lab + NSCL … by a nuclear reactionfor example: 208Pb + 9Be -> 197Au + p + …. Makes gold from lead… at a very slow rate (20,000 nuclide/sec)

  22. Iron from a previous generation of stars is exposed to a flux of neutrons • How does this create heavy elements ? • Neutron Capture Processes There are 2: - s-process (slow neutron capture) - r-process (rapid neutron capture) Do neutron capture process exercise

  23. Where does the s-process happen ? there ! in red giants – and it takes several million years ! (or, low mass TP-AGB stars) AGB = Asymptotic Giant Branch TP=Thermally Pulsing

  24. How can we tell ? Analyze light from a red giant: Star contains Technetium (Tc) !!!(heavy element Z=43, T1/2 4 Mio years, Merrill 1952)

  25. 197Au: Au has 79 protons197Au has 197 – 79 = 118 neutrons Gold (197Au) number of protons ? Helium number of neutrons Hydrogen

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