Asia Pacific Physics Week 2023 (APPW2023)

Monday, Nov. 6, 2023

4:00 PM - 4:30 PM  C. N. Yang Award Talk  Liyong Zhang (Beijing Normal University) 

How calcium was produced in the oldest stars

Liyong Zhang

College of Nuclear Science and Technology, Beijing Normal University, Beijing

The production of calcium in the First Stars (Pop III Stars), which formed out of the primordial matter of the Big Bang, remain most fascinating mysteries in astrophysics. Advanced nuclear burning and supernovae were thought to be the dominant source of the Ca production seen in all stars. This talk will report a different path to Ca production through the breakout from the carbon-nitrogen-oxygen (CNO) cycle.

19F(p,g)20Ne is a key breakout reaction among the reaction chains through which the First stars synthesis Ca from the light isotopes such as CNO. We extend the direct measurement of this reaction down to an unprecedentedly low energy of 186 keV, and discovered a new resonance at 225 keV. Due to this new resonance, the measured 19F(p,g)20Ne reaction rate is 7.4 times larger than the previous prediction. This results in a stronger breakout during stellar hydrogen burning, and may reveal the nature of Ca production in Pop III stars imprinted on the oldest known ultra-iron poor star, SMSS0313-6708.

The experiment was performed at the Jinping Underground Nuclear Astrophysics (JUNA) facility situated in China Jinping Underground Laboratory (CJPL), the deepest laboratory in the world, offering an environment with extremely low cosmic-ray induced background. The result has far-reaching implications on our understanding of how the first stars evolve and die. Our rate underscore the influence that faint supernovae from Pop III stars can have on the nucleosynthesis observed in the oldest known stars and first galaxies, key mission targets of the James Webb Space Telescope.