Q

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Quasars Cosmology
Quasars and Cosmology
ASTR-1510-01 ASTR-1510-02
Department of Physics, Applied Physics
Astronomy, RPI
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Week 12

• The Early Universe II
• t1 second to t3 minutes
• Jones Lambourne
• Sections 6.4-7
• November 16, 2009
• 300 PM
• Darrin 330

Department of Physics, Applied Physics
Astronomy, RPI
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Outline

• Review The First Second
• Elemental Abundances in the Universe
• Nucleosynthesis in the Early Universe
• Nucleosynthesis in Stars

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bosons

Image Stanford/SLAC
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Review The First Second of Time

• 0 sec lt t lt 10-44 sec - Planck Epoch
• Interactions 1 (gravitystrongweakEM)
• Particles Unknown! Superstrings?
• Starts The Big Bang.
• Ends Gravity force decouples.
• 10-44 sec lt t lt 10-36 sec - GUT Epoch
• Interactions 2 (gravity, strongweakEM)
• Particles False vacuum.
• Starts Gravity force decouples.
• Ends Strong force decouples.

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The First Second (contd)

• 10-36 sec lt t lt 10-34 sec Inflation
• Interactions 3 (gravity, strong, weakEM)
• Particles free quarks, leptons, bosons
  antiparticles.
• Starts Strong force decouples, inflation begins
• Ends Inflation ends.
• Phase transition vacuum jumps to lower energy
  state.
• Energy released fuels exponential expansion.
• Universe grows by factor 1050!
• Vacuum energy released also forms all known
  particles.
• Very slight (10-9) matter/antimatter asymmetry.

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The First Second (contd)

• 10-34 sec lt t lt 10-12 sec The Particle Desert
• Interactions 3 (gravity, strong, weakEM)
• Particles free quarks, leptons, bosons
  antiparticles.
• Starts Inflation ends.
• Ends Weak force decouples.
• 10-12 sec lt t lt 10-5 sec
• Interactions 4 (gravity, strong, weak, EM)
• Particles free quarks, leptons, bosons
  antiparticles
• Starts Weak force decouples.
• Ends free quarks form hadrons (protons,
  neutrons).

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The First Second (contd)

• 10-5 sec lt t lt 1 sec Hadron Epoch
• Interactions 4 (gravity, strong, weak, EM)
• Particles protons, neutrons, leptons, photons
• Starts free quarks form hadrons.
• Ends neutrinos decouple.
• Protons (p), neutrons (n) annihilate with
  antiparticles.
• Tiny matter excess yields some n and p
  leftovers!
• Neutrino reactions converted n into p and vice
  versa,
• ne p n e
• but protons were favored, protonsneutrons 51.

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The Elements and Their Isotopes
Z no. protons, N no. neutrons
Element nuclei with the same Z (carbon
Z6). Example all carbon nuclei have Z6
protons. Isotopes nuclei with same Z but
different N. Example carbon can have N6, N7,

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Periodic Table of Chemical Elements
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Cosmic Abundances of the Elements
Number of protons in nucleus
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Temperature (T) Particle Energy
At t1 sec, the energies are about right for
nuclear reactions. Were all of the elements made
in this way?
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Reactions of the Light Elements
5
4
3
Z
2
dashedunstable
1
0
5
6
7
0
1
2
3
4
N
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Big Bang Nucleosynthesis (BBN)

• Problem 1 free neutrons unstable.
• Problem 2 universe is expanding and cooling!
• MUST WORK FAST (3 MINUTES)
• Problem 3 no stable nuclei of atomic mass 5, 8.
• CANNOT GET PAST LITHIUM.
• Hey, its not all bad
• BBN EXPLAINS WHY UNIVERSE IS
• MOSTLY HYDOGEN, HELIUM!

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A Simulation of BBN
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Simulated vs. Actual Abundances
4He
actual

• Simulations depend on Wb baryonic
  density/critical density.
• Actual abundances require Wb between 0.02 and
  0.03.

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Origin of Elements Heavier than Li

• BBN seeds the Universe with H, He, Li.
• Galaxies and stars form from primordial gas.
• Stars fuse light elements into heavier elements.
• This happens VERY SLOWLY.
• 10 billion yr. for a star like the Sun.
• 10 million yr. for much heavier stars.
• Some dead/dying stars release products back into
  space, enriching the interstellar gas.
• Later generations form from enriched gas.
• And the cycle repeats

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Hydrogen Fusion in Stars

• Main sequence stars like the Sun consume H to
  make He by a variety of fusion reactions
  collectively known as hydrogen burning.
• There are 2 H-burning processes
• pp chain (dominant in Sun-like stars)
• CNO cycle (dominant in heavy stars)

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The Proton-Proton (PP) Chain

• The first reaction is pretty inefficient, but
  once d is formed the reaction proceeds rapidly.
• For second reaction T gt 106 K
• Energy released as KE, photons, neutrinos by
  annihilation of e

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CNO Cycle

• Net Result 12C 4p 12C 4He

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Beyond Helium

• Helium Burning
• 4He 4He 4He 12C
• CNO Cycle
• 12C 14N
• Carbon Burning
• 12C , 12C 20Ne, 23Na, 24Mg
• And so on

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Summary Nucleosynthesis in stars.
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Summary Origin of the Elements

• Vacuum Phase Transition (10-36 sec)
• energy released forms free quarks, leptons,
  bosons ( every particle)
• matter/antimatter asymmetry
• Quark-Hadron Transition (10-5 sec)
• free quarks combine to (mostly) protons
  neutrons
• Big Bang Nucleosynthesis (t1 sec)
• makes H, He, and Li
• Stellar Nucleosynthesis
• makes all the other natural elements