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Creation of new elements is energy source of stars (and the sun) We are made of star stuff…. Carl Sagan.

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Presentation on theme: "Creation of new elements is energy source of stars (and the sun) We are made of star stuff…. Carl Sagan."— Presentation transcript:

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2 Creation of new elements is energy source of stars (and the sun) We are made of star stuff…. Carl Sagan

3 The sun shines3.85e33 erg/s = 3.85e26 Wattsfor at least ~4.5 bio years The entire sun made of coal would last ~ 4000 years

4 Nucleus Factories

5 Question 3 How were the elements from iron to uranium made ? (main question: r-process) Question 3 How were the elements from iron to uranium made ? (main question: r-process) Committee for the Physics of the Universe (NRC/NAS) Connecting Quarks with the Cosmos – 11 science questions for the new century

6 Periodic Table of Elements in nature

7 Elements in nature Made in the Big Bang

8 Elements in nature Made by fusion in stars…

9 Elements in nature How are the elements heavier than iron made?

10 Hydrogen burning 7Mio yrs Hydrogen (1p,0n)Helium (2p, 2n) Helium burning 700,000 yrs Helium (2p,2n)Carbon (6p, 6n), Oxygen (8p,8n) Carbon(+Ne) burning 400 yrs Carbon (6p,6n)Oxygen (8p,8n) Oxygen burning 8 months Oxygen (8p,8n)Silicon (14p,14n) Silicon burning 1 day Silicon (14p,14n)Nickel (28p,28n) Burning stages of a 25 solar mass star initially present: mostly hydrogen (~70% - from big bang)

11 For stable nuclei !!! Average binding energy per nucleon (MeV)

12 Window of the Protestant church in Wixhausen, Germany

13 Precollapse structure of massive star Iron core collapses and triggers supernova explosion

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15 Atomic Nucleus Proton Neutron

16 Observed Nuclei in the Universe: Hydrogen: Mass number = 1 Helium: Mass number = % 8.9% What is the universe made of? Iron ?

17 What is the Universe made of?

18 Gold: 79 protons neutrons Mass number = 197 Iron: 26 protons + 30 neutrons Mass number = 56

19 Gold ( 197 Au) Helium Hydrogen number of protons number of neutrons 197 Au: Au has 79 protons 197 Au has 197 – 79 = 118 neutrons

20 Gold ( 197 Au) Helium Hydrogen number of protons number of neutrons 197 Au: Au has 79 protons 197 Au has 197 – 79 = 118 neutrons

21 So how is gold made ? Some earlier failed attempts (1590) Alchemists lab + NSCL NSCL (present day) … by a nuclear reaction for example: 208 Pb + 9 Be -> 197 Au + p + …. Makes gold from lead… at a very slow rate (20,000 nuclide/sec) … by Alchemy: For example: with the Philosophers Stone Making gold/silver from base metals

22 Iron from a previous generation of stars is exposed to a flux of neutrons How does this create heavy elements ? Neutron Capture Processes There are 2: - s-process (slow neutron capture) - r-process (rapid neutron capture) Do neutron capture process exercise

23 Where does the s-process happen ? there ! in red giants – and it takes several million years ! (or, low mass TP-AGB stars) AGB = Asymptotic Giant Branch TP=Thermally Pulsing

24 How can we tell ? Analyze light from a red giant: Star contains Technetium (Tc) !!! (heavy element Z=43, T 1/2 4 Mio years, Merrill 1952)

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26 Gold ( 197 Au) Helium Hydrogen number of protons number of neutrons 197 Au: Au has 79 protons 197 Au has 197 – 79 = 118 neutrons ?

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