1. Nucleosynthesis and formation of the elements

3. Cosmic abundance of the elements
Mass number

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

5. In the seconds following the Big 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

7. Diagramme Hertzprung-Russel

8. 1st Generation Stars - H fusion and production of 4He
1H + 1H  2H + b+ + v MeV
2H + 1H  3He + g MeV
3He + 3He  4He + 1H + 1H MeV

9. 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

10. He Fusion in Red Giants (~ 106 to 107 years)
4He + 4He  8Be
8Be + 4He  12C + g
12C burning (<1000 years)
12C + 4He  16O
12C + 12C  20Ne + 4He + g
16O burning (<1 year)
16O + 16O  28Si + 4He + g
12C + 16O  24Mg + 4He + g

11. End of a Red Giant's life: Si combustion: lasts 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 . . .

12. 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 > 90
(uranium and transuranics)

13. Supernova and 2nd generation stars

14. Supernova remnants Cygnus Loop (HST): green=H, red=S+, blue=O++
Cas A in x-rays (Chandra)
Vela
Remnant of SN386, with central pulsar (Chandra)
SN1998bu

15. Nucleosynthesis by n and p capture

16. Elements > Fe: neuton activation
CNO
Fe: produced
in the final
stage of fusion
Equilibrium
burning
Elements > Fe: neuton activation
in supernova Mg Ar Na Al Cr P Ti Mn Cl
Fissionable Elements K Co F V
Instable