Nucleosynthesis and the Origin of the Elements •Big Bang Nucleosynthesis = mainly H and He •Stellar Nucleosynthesis = elements up to Fe formed within stars •Supernova = produces heaviest elements and disseminates all
http://hubblesite.org/gallery/album/pr2001009b/
1 2 Big Bang Nucleosynthesis = mainly H and He
10-32 sec 14 sec 40 min 7.0 x 105 years
Time
+ + quarks H (75%) + etc. He (25%) + + trace 2H, 3He, + and 5Li
3 x 109 3000
Temperature (K)
Stellar Nucleosynthesis - Elemental Abundances in the Solar System
Big Bang Stellar Nucleo. Supernova
12 H 10 He 8 Fe 6
4
2
0
Logarithm of Abundance B Sc -2 Li Be -4
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81
Mass-5 (Be) and Atomic Number mass-8 (O) “bottleneck”
3 Number of Stable Nuclides as a function of Even vs. Odd
Number of A Z stable nuclides
Even Even 157
Even Odd 4
Odd Even 53
Odd Odd 50
264 total
Stellar Nucleosynthesis - The Origin of the Elements
H-burning unburned H H-burning H He C Ne O
Si
unburned H unburned He He-burning
Name of Process Fuel Products Temperature (K) Lifetime Remaining 1. H-burning H He 60 x 106 10,000,000 years 2. He-burning He C, O 200 x 106 1,000,000 years 3. C-burning C O, Ne, Na, Mg 800 x 106 1,000 years 4. Ne-burning Ne O, Mg 1500 x 106 10 years 5. O-burning O Mg to S 2000 x 106 1 year 6. Si-burning Mg to S Elements near Fe 3000 x 106 1 day 7. Rapid Neutron Capture neutrons Elements after Fe supernova 1 sec
4 1. Hydrogen Burning to form He
1. Two H-nuclei (protons) react to form a 1 1 2 0 deuterium nucleus (1 proton and 1 neutron) 1H1H1D 1e
3 2. The deuterium captures a proton to form 2 He 2 1 3 (2 protons and 1 neutron) 1D1H2 He
4 3. Two nuclei combine to form 2 He 3 3 4 1 (2 protons and 2 neutrons) plus the release of 2He2He2 He21H two protons 4. Energy is released in each step in the form of gamma rays, neutrinos, etc – star heats up
+ + + + + + + + + + + + + + + neutron + + proton
Helium can also be Produced via the CNO Cycle
12 1 13 1. 6 C1H 7 N
2. 13 13 0 1. start 7N 6 C 1e
3. 13 1 14 6 C1H 7 N
14 1 15 4. 7N1H 8 O
15 15 0 5. 8 O 7 N 1e
15 1 12 4 6. 7N1H 6 C2He
http://upload.wikimedia.org/wikipedia/commons/0/06/CNO_Cycle.png
5 2. Helium Burning to form C and O
A. triple-alpha process to form C the key to all the syntheses needed to form elements beyond He H He C 4 4 8 Very unstable – Ne He He Be decays in only O 2 2 4 10-16 sec Si 8 4 12 4 Be2He 6 C
B. alpha process to form O
12 4 16 6C2He 8 O
3. Carbon Burning to form O, Ne, Na, Mg
12 12 16 4 6C 6C 8 O 22 He H He C 12 12 20 4 Ne 6C 6C10Ne2He O
Si 12 12 23 1 6C 6C11Na1H
12 12 23 1 6C 6C12Mg 0n
6 4. Neon Burning to form Oxygen and Magnesium
20 16 4 H 10Ne 8 O2He He C Ne 20 4 24 O 10Ne2He12Mg Si
5. Oxygen Burning to form Magnesium Sulfur
16 16 24 4 8O 8O12Mg 22 He H He C Ne 16 16 28 4 O 8O 8O14Si 2He Si 16 16 31 1 8O 8O15P1H
16 16 31 1 8O 8O16S0n
7 6. Silicon Burning to form Elements Near Fe
Successive alpha processes -
H 28 4 32 He 14Si 2He16S C Ne O 32 4 36 16S2He18Ar Si
36 4 40 18Ar 2He20Ca 48 4 52 24Cr2He26Fe
7. Rapid Neutron Capture* - Heavy Elements After Fe e.g. s-process, r-process
*there is also a p-process where protons are added
8 Formation of The Solar System
http://ircamera.as.arizona.edu/NatSci102/Na tSci102/lectures/solarsysform.htm
9 Elemental Composition of the Planets The Inner Planets
Elemental Composition of the Planets The Gas Giants
10 Structure and Composition of the Earth
Mohorovicic Discontinuity Silicate minerals Plastic flow
Liquid outer core
Solid inner core
Al Fe Si K
Na
O other
11 12