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Heavy Element Nucleosynthesis s-process r-process p-process

Hydro Static Nucl. NSE Iron Group. Heavy Element Nucleosynthesis s-process r-process p-process. How do we explain obs.?. If universe ~14 Gyr old Where’d we get so much H & He??? pp-chain is too slow massive stars burn beyond He Stars must have been born with that H & He

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Heavy Element Nucleosynthesis s-process r-process p-process

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  1. Hydro Static Nucl. NSE Iron Group Heavy Element Nucleosynthesis s-process r-process p-process

  2. How do we explain obs.? • If universe ~14 Gyr old • Where’d we get so much H & He??? • pp-chain is too slow • massive stars burn beyond He • Stars must have been born with that H & He • Big bang nucleosynthesis

  3. Info for any nucleosynthesis calculation • What building blocks are available? • n, p, nuclides, e, g, n, etc… • What are the reaction time scales? • Related to rxn rates: t = 1/G • What are the dynamical time scales? • Hydro-static EQ; no time scale • Free-fall time t = finite

  4. Cosmology First published in Weltall and Menschheit (1907) edited by Hans Kraemer

  5. Tenets of Modern Cosmology • Cosmological Principle • Universe is homogeneous • looks the same anywhere we go • Universe is isotropic • looks the same any direction we look • Laws of physics are the same everywhere(when)

  6. Tenets of Modern Cosmology • General Relativity • theory of gravity • Standard Model of Particle Physics • Constituents of normal matter • Interactions between them

  7. Tenets of Modern Cosmology Dark Side of Cosmology • Dark Matter • Dark Energy Courtesy of George Lucas

  8. Working back to the big bang • GR predicts universe is expanding • Einstein tried to fix this with L • Claims its his biggest mistake • Hubble obs. recession of galaxies (1929) • First evidence for universal expansion • Subsequent obs. confirm this

  9. Working back to the big bang • If the universe is expanding…. • What was it like in the past? • What happens to its constituents? • Baryons- n, p, nuclides • Smaller • Hotter • Denser

  10. Initial Conditions • At kT>1 MeV • Thermal equilibrium • Chemical equilibrium • Main constitients • Photons • Neutrinos • Electrons/positrons • Small number of baryons (n & p) } NSE

  11. Relevant timescales • Dynamical timescale • Hubble expansion rate H ~ T2/MP • Reaction timescales • Weak interaction GW ~ T5/MW4 • Rxn rates Grxn~ rBlrxn

  12. Big bang nucleosynthesis • When T~1 MeV • GW~H weak rates become slow • n’s stop interacting • Electrons/positrons become NR • e+ + e- 2g • energy goes into all but n’s • Tg > Tn

  13. Big bang nucleosynthesis • n,p would like to fuse into d • But Ng(E>Bd) >> NB • So as soon as d is made, it is destroyed • Gdiss >> Gfus • So we must wait….. • Called the D bottleneck • while we wait, n’s decay

  14. Big bang nucleosynthesis • T~70 keV, d not efficiently destroyed • So……. p(n,g)d(p,g)3He(d,p)4He • We convert H into 4He (all n’s go into 4He) • Sometimes we even 3He(a,g)7Be • T~40 keV, Coulomb barrier halts nucl.

  15. Light Element Abundances • 4He: known syst. Olive & Skillman 2004 • D: few obs. systems Burles, Kirkman, O’Meara • 3He: extrap. error Bania et al, Vangioni-Flam et al • 7Li: add. syst.? Spite & Spite, Ryan et al, Bonifacio et al • WMAP CMB WBh2 Bennet et al, Spergel et al

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