stable Elements in nature 75 in mass after

(stable) Elements in nature 75% in mass after the Big Bang 25% in mass ~0. 00000001 % : More than 75% made in r-process

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

Nucleus Factories

Creation of new elements is energy source of stars (and the sun)

The sun shines 3. 85 e 33 erg/s = 3. 85 e 26 Watts for at least ~4. 5 bio years The entire sun made of coal would last ~ 4000 years

On the way to making gold: Burning stages of a 25 solar mass star initially present: mostly hydrogen (~70% - from big bang) Hydrogen burning 7 Mio yrs Hydrogen (1 p, 0 n) Helium (2 p, 2 n) Helium burning 700, 000 yrs Helium (2 p, 2 n) Carbon (6 p, 6 n), Oxygen (8 p, 8 n) Carbon(+Ne) burning 400 yrs Carbon (6 p, 6 n) Oxygen (8 p, 8 n) Oxygen burning 8 months Oxygen (8 p, 8 n) Silicon (14 p, 14 n) Silicon burning 1 day Silicon (14 p, 14 n) Iron (26 p, 30 n)

For stable nuclei !!!

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

Is the universe made of iron ? Nuclei in the Universe: 91. 0% Iron ? 8. 9% Hydrogen: Mass number = 1 Helium: Mass number = 4

… not yet Iron: Gold: 26 protons + 30 neutrons 79 protons + 118 neutrons Mass number = 56 Mass number = 197

So how is gold made ? Some earlier failed attempts (1590) NSCL Alchemists lab + NSCL … by a nuclear reaction for example: 198 Hg + 9 Be -> 197 Au + p + …. Makes gold from mercury

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

Where does it happen ? there ! in red giants – and it takes several million years ! (or, more correctly, low mass TP-AGB stars)

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)

The s-process makes only half of all heavy elements so where does the rest come from ?

Question 3 How were the elements from iron to uranium made ?

Pt Xe

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

Where does the r-process happen ? We don’t know – here are some ideas: Supernovae ? Neutronstar merger ?

r-process: status and reach of (some) RIB facilities r-process Pb RIA Reach Fe NSCL/MSU Reach Known halflife

Towards the future: The Joint Institute for Nuclear Astrophysics: http: //www. jinaweb. org The Rare Isotope Accelerator (RIA) at MSU ?