GEOL3045: Planetary Geology
GEOL3045: Planetary Geology
Lysa Chizmadia11 Jan 2007
The Big Bang & Nucleosynthesis
Lysa Chizmadia11 Jan 2007
The Big Bang & Nucleosynthesis
IntroductionIntroduction Parts of an atom:
Protons (p+): +’ly charged particles in nucleus, mass ~ 1 atomic mass
Neutrons (n0): 0 charged particles in nucleus, mass ~ 1 atomic mass
Electrons (e-): -’ly charged particles in nucleus, mass = 5.45 x 10-4 atomic masses [= 1/ 1836 of p+ mass]
Definition of an isotope: Different # of n0s Same element, different atomic mass E.g. Oxygen
16O = 8 p+s and 8 n0s 17O = 8 p+s and 9 n0s 18O = 8 p+s and 10 n0s
Parts of an atom: Protons (p+): +’ly charged particles in nucleus,
mass ~ 1 atomic mass Neutrons (n0): 0 charged particles in nucleus,
mass ~ 1 atomic mass Electrons (e-): -’ly charged particles in nucleus,
mass = 5.45 x 10-4 atomic masses [= 1/ 1836 of p+ mass]
Definition of an isotope: Different # of n0s Same element, different atomic mass E.g. Oxygen
16O = 8 p+s and 8 n0s 17O = 8 p+s and 9 n0s 18O = 8 p+s and 10 n0s
The Big BangThe Big Bang Initially universe
Only contains photons (), p+s, n0s, e-s and e+s
Due to high , particles collide Pair production Annihilation Proton - Neutron Conversion
Initially universe Only contains photons (), p+s, n0s, e-s
and e+s Due to high , particles collide
Pair production Annihilation Proton - Neutron Conversion
Images from: http://aether.lbl.gov/www/tour/elements/early/early_a.html
Nucleosynthesis (H & He)Nucleosynthesis (H & He) Due to T, particles don’t stick
With T, particles stick to form elements
2 Pathways to form H & He:
Due to T, particles don’t stick
With T, particles stick to form elements
2 Pathways to form H & He:
Images from: http://aether.lbl.gov/www/tour/elements/early/early_a.html
Pathway #1
Pathway #2
Nucleosynthesis (Li & Be)Nucleosynthesis (Li & Be)
6Li = 4He + 2H 7Li = 4He + 3H 7Be = 3He + 4He 8Be = 4He + 4He
Finally, cools enough for atoms to capture e- to be neutral
6Li = 4He + 2H 7Li = 4He + 3H 7Be = 3He + 4He 8Be = 4He + 4He
Finally, cools enough for atoms to capture e- to be neutral
Images from: http://aether.lbl.gov/www/tour/elements/early/early_a.html
Big Bang NucleosynthesisBig Bang Nucleosynthesis
So where do the heavier elements originate? So where do the heavier elements originate?Image from: http://aether.lbl.gov/www/tour/elements/element.html
Produced during Big Bang
Stellar NucleosynthesisStellar Nucleosynthesis Initially ~75% H & ~25% He Not homogeneously distributed Places of , become clumps
Clumps collapse into nebulae Nebula collapses into star
T, P and
Initially ~75% H & ~25% He Not homogeneously distributed Places of , become clumps
Clumps collapse into nebulae Nebula collapses into star
T, P and
Images from: http://aether.lbl.gov/www/tour/elements/stellar/stellar_a.html
Stellar NucleosynthesisStellar Nucleosynthesis Inside star’s core:
P & very high Nuclear fusion H-burning: H He Mass > 1.5 M,
He-burning: He C
Inside star’s core: P & very high Nuclear fusion H-burning: H He Mass > 1.5 M,
He-burning: He C
Images from: http://en.wikipedia.org/wiki/Main_sequence and http://aether.lbl.gov/www/tour/elements/stellar/stellar_a.html
= Sunlight
Stellar EvolutionStellar Evolution Hertzsprung-Russell
diagram Mass > 4 M
H He C Ne O Si Fe
Hertzsprung-Russell diagram Mass > 4 M
H He C Ne O Si Fe
Images from: http://en.wikipedia.org/wiki/Main_sequence
Nucleosynthesis ReactionsNucleosynthesis Reactions Mass > 4 M,
C-burning 12C + 12C 20Ne +
4He
23Na + 1H 24Mg + n0
Mass > 8 M, Ne-burning:
20Ne + 16O + 4He 20Ne + 4He 24Mg +
Mass > 4 M,
C-burning 12C + 12C 20Ne +
4He
23Na + 1H 24Mg + n0
Mass > 8 M, Ne-burning:
20Ne + 16O + 4He 20Ne + 4He 24Mg +
O-burning 16O + 16O 28Si + 4He
31P + 1H
31S + n0
31P + 1H
30S + 21H
30P + 22H
Mass = 8-11 M,
Si-burning 12C 16O 20Ne 24Mg
28Si 32S 36Ar 40Ca 44Ti 48Cr 52Fe 56Ni
56Ni decays to 56Co 56Fe
t1/2 = 6 days & 77 days
O-burning 16O + 16O 28Si + 4He
31P + 1H
31S + n0
31P + 1H
30S + 21H
30P + 22H
Mass = 8-11 M,
Si-burning 12C 16O 20Ne 24Mg
28Si 32S 36Ar 40Ca 44Ti 48Cr 52Fe 56Ni
56Ni decays to 56Co 56Fe
t1/2 = 6 days & 77 days
What about elements > Ni?
NucleosynthesisNucleosynthesis
So where do the heavier elements originate? So where do the heavier elements originate?
Image from: http://aether.lbl.gov/www/tour/elements/element.html
Produced during Big BangStellar Nucleosynthesis
Fe has highest binding EFe has highest binding E All elements up to Fe release
energy (E) when formed (exothermic)
Heavier elements need more energy added (endothermic)
How to add more E to form heavier elements?
All elements up to Fe release energy (E) when formed (exothermic)
Heavier elements need more energy added (endothermic)
How to add more E to form heavier elements?Image from: http://en.wikipedia.org/wiki/Silicon_burning_process
SupernovaeSupernovae With burning of heavier elements,
star continues to collapse Fe breaks down to 4He, n0 and p+
Finally no more compression possible
Outer layers bounce off core Supernova occurs Releases neutrons
With burning of heavier elements, star continues to collapse
Fe breaks down to 4He, n0 and p+
Finally no more compression possible
Outer layers bounce off core Supernova occurs Releases neutrons
Images from: http://aether.lbl.gov/www/tour/elements/stellar/stellar_a.html
Supernovae ProcessesSupernovae Processes R-process: rapid neutron capture
Occurs over seconds S-process: slow neutron capture
Occurs over 1000s of years P-process: knocks out neutrons
Results in proton-rich isotopes rP-process: rapid proton capture
Occurs over seconds Cannot progress > Te
R-process: rapid neutron capture Occurs over seconds
S-process: slow neutron capture Occurs over 1000s of years
P-process: knocks out neutrons Results in proton-rich isotopes
rP-process: rapid proton capture Occurs over seconds Cannot progress > Te
Image from: http://en.wikipedia.org/wiki/S-process
Chart of the NuclidesChart of the Nuclides
Red = stable Blue = extremely
short half lives
For more info: http://en.wikipedia.org/wiki/Isotope_table_
%28complete%29
Red = stable Blue = extremely
short half lives
For more info: http://en.wikipedia.org/wiki/Isotope_table_
%28complete%29
Image from: http://en.wikipedia.org/wiki/Main_sequence
SummarySummary 1) Only H, He, Li & Be produced during Big
Bang Initially only energy & sub-atomic particles existed With T, particles collided to form atoms
2) Elements up to Fe produced by stellar nucleosynthesis Larger star produce heavier elements
3) All elements heavier than Fe produced in supernovae Neutron capture Proton capture
1) Only H, He, Li & Be produced during Big Bang Initially only energy & sub-atomic particles existed With T, particles collided to form atoms
2) Elements up to Fe produced by stellar nucleosynthesis Larger star produce heavier elements
3) All elements heavier than Fe produced in supernovae Neutron capture Proton capture