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 neutron + proton 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 .