Energy and Breakout from the (Hot) CNO Cycle University of York (Replace with institution name) Proton number (Z) Neutron number (N) Chart from: http://people.physics.anu.edu.au/~ecs103/chart/index.php Nuclear physics in stars The CNO cycle – catalysts for stars HotCNO Where do heavy elements come from? Breakout to make heavy nuclei

Nuclei and decay modes Nuclei: bound collections of neutrons and protons Mass of nuclei Binding energy Proton number (Z) Decay modes: Beta decay (beta+ or beta- ) Alpha decay Fission Proton emission Neutron emission Neutron number (N)

4⨉H → 4He + 2⨉νe + 2⨉β+ + E Why does the sun shine? Where does its energy come from? Image above from: https://www.nasa.gov/content/goddard/sun release-x3.1-class-solar-flare-on-oct-24-2014 4⨉H → 4He + 2⨉νe + 2⨉β+ + E Heard of the proton-proton chain? The CNO cycle?

(p,α) Carbon as a catalyst for hydrogen fusion CNO cycle Carbon as a catalyst for hydrogen fusion Neutron number (N) Proton number (Z) (p,α) The CNO cycle – most stars do this…

…happens in hot astrophysical sites e.g. X-ray bursters Novae Hot CNO Activity…. …happens in hot astrophysical sites e.g. X-ray bursters Novae https://www.nasa.gov/mission_pages/galex/image-galex-nova-20070307.html

Hot CNO Activity….

Hot CNO Activity….

Hot CNO Activity….

Questions Where did you get stuck? Did anyone end up back at the same place? In groups… Can you find all three H-CNO loops? Draw the loops – different colour for each process What are the nuclear processes involved? What were the catalyst nuclei in each loop? For the loop, what has been lost (from the star), what has been gained? Where did you get stuck? Why don’t 14O and 15O absorb 1H?

How are Heavier Elements Formed? Image top left left from: https://www.nasa.gov/mission_pages/galex/image-galex-nova-20070307.html Image right from: https://www.nasa.gov/multimedia/imagegallery/image_feature_2173.html X-ray bursts Breakout from catalytic hydrogen fusion Igniting the rapid proton capture process Supernovae or neutron-star mergers: the site for rapid neutron-capture? Creation of iron-group elements in massive stars Helium fusion (triple-alpha)

Breakout from HCNO – creating heavier elements Image top left left from: https://www.nasa.gov/mission_pages/galex/image-galex-nova-20070307.html X-ray bursts Breakout from catalytic hydrogen fusion Igniting the rapid proton capture process Add an alpha particle to 15O BREAK-OUT!

Breakout from HCNO – creating heavier elements Image top left left from: https://www.nasa.gov/mission_pages/galex/image-galex-nova-20070307.html X-ray bursts Breakout from catalytic hydrogen fusion Igniting the rapid proton capture process An 18Ne nucleus absorbs an alpha particle and emits a proton. BREAK-OUT!