Nucleosynthesis Woodstock Well I came across a child of God, he was walking along the road and I asked him tell where are you going, this he told me: Well, I’m going down to Yasgur's farm, going to join in a rock and roll band. Got to get back to the land, set my soul free. We are stardust, we are golden, we are billion year old carbon, and we got to get ourselves back to the garden. - Crosby, Still, Nash and Young

Nucleosynthesis We have already described many of the reactions that produce elements up through iron. Beyond iron, heavier elements are synthesized through neutron capture.

AZ X + n  A+1Z Y Nucleosynthesis We have already described many of the reactions that produce elements up through iron. Beyond iron, heavier elements are synthesized through neutron capture. AZ X + n  A+1Z Y

AZ X + n  A+1Z Y Nucleosynthesis We have already described many of the reactions that produce elements up through iron. Beyond iron, heavier elements are synthesized through neutron capture. AZ X + n  A+1Z Y Neutron capture is fairly “slow” process. s-process: The relatively slow process of neutron capture.

AZ X + n  A+1Z Y Nucleosynthesis We have already described many of the reactions that produce elements up through iron. Beyond iron, heavier elements are synthesized through neutron capture. AZ X + n  A+1Z Y After (possible multiple) neutron capture, the isotope can become unstable.

AZ X  AZ+1 Y + 0-1 + photon Nucleosynthesis The isotope can then undergo beta decay, forming an element “higher” on the periodic table.  emission: The beta particle is an electron ( 0-1 ) AZ X  AZ+1 Y + 0-1 + photon

Nucleosynthesis Neutron capture and radioactive decay can account for the formation of most of the heavier elements. The heaviest elements are believed to be created by a different process than the s-process. The neutron rich environment can result in rapid multiple neutron capture. r-process: the rapid capture of neutrons by nuclei during a supernova event.

Nucleosynthesis See Figure 21.18 What is the evidence? Light curves of a supernova event. Recall: The light curves will mimic the radioactive decay of unstable elements. Observed light curves do, in fact, mimic the radioactive decay of known elements. See Figure 21.18

Nucleosynthesis This figure shows the relative abundances resulting from a calculation of the explosive burning of silicon (shown as crosses and dashed lines) compared to the actual abundances (shown as solid squares and lines) observed throughout the cosmos. The crosses are very close to the squares for the more abundant elements (such as Si, S, Ar, Ca, Cr, Fe), giving us confidence that these elements can be produced in the observed ratios by such reactions.