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