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Overview of Nucleosynthesis in Elements: Processes, Time Scales, and Cosmic Evolution

Delve into the synthesis of heavy elements in stars, understanding cosmic origins of hydrogen and helium, reaction time scales, and implications of nucleosynthesis in the universe's evolution. Explore the tenets of modern cosmology, dark matter, and energy, alongside the dynamics of the expanding universe from the big bang. Discover the relevant time scales, including dynamical and Hubble expansion rates, weak interaction, and reaction timescales in the context of nucleosynthesis developments. Examine the light element abundances and insights from observational data like WMAP.

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Overview of Nucleosynthesis in Elements: Processes, Time Scales, and Cosmic Evolution

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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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