Nucleosynthesis and formation of the elements

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Nucleosynthesis and formation of the elements
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Cosmic abundance of the elements
Mass number
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Nucleosynthesis

• Big Bang ca 12 000 Ma
• Supernova ca 5 000 Ma
• Condensation of matter and formation of the known
  elements . . .

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In the seconds following theBig Bang

• Condensation of matter into p and n
• Formation of the fuel of the stars . . . H et He
• T ? 3 x 109 K
• p e ? n v
• 1H n ? 2H g
• 2H p ? 3He g
• 3He n ? 4He g

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Diagramme Hertzprung-Russel
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1st Generation Stars - H fusion and production
of 4He

• 1H 1H ? 2H b v 0.422 MeV
• 2H 1H ? 3He g 5.493 MeV
• 3He 3He ? 4He 1H 1H 12.859 MeV

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2nd Generation Stars(Our sun today)Fusion by
CNO reaction

• 12C 1H ? 13N g
• 13N ? 13C b v
• 13C 1H ? 14N g
• 14N 1H ? 15O g
• 15O ? 15N b v
• 15N 1H ? 12C 4He

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He Fusion in Red Giants ( 106 to 107 years)
4He 4He ? 8Be 8Be 4He ? 12C g
12C burning (lt1000 years)
12C 4He ? 16O 12C 12C ? 20Ne 4He g
16O burning (lt1 year)
16O 16O ? 28Si 4He g 12C 16O ? 24Mg 4He
g
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End of a Red Giant's life Si combustionlasts
about 1day
28Si 4He ? 32S g 32S 4He ? 36Ar g
36Ar 4He ? 40Ca g 40Ca 4He ? 44Ti g ?
44Ca 2b 44Ti 4He ? 48Cr g ? 48Ti
2b 48Cr 4He ? 52Fe ? 52Cr 2b 52Fe 4He ?
56Ni g ? 56Fe 2b 56Ni / 56Fe 4He ?
impossible . . .
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Nuclear binding energy maximum

• maximum at 56Fe
• after, fusion becomes endothermic
• nucleosynthesis beyond 56Fe is by neutron
  capture
• and by fission of nuclides with Z gt 90
• (uranium and transuranics)

http//www.chem.uidaho.edu/honors/nucbind.html
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Supernovaand 2nd generation stars
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Supernova remnants
Cygnus Loop (HST) greenH, redS, blueO
Cas A in x-rays (Chandra)
Vela
Remnant of SN386, with central pulsar (Chandra)
SN1998bu
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Nucleosynthesis by n and p capture
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CNO
Fe produced in the final stage of fusion
Equilibrium burning
Elements gt Feneuton activation in supernova
Mg
Ar
Al
Cr
Na
Ti
P
Mn
Fissionable Elements
Cl
K
Co
F
V
Instable
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