Science and Technology Daily reporter Zhang Gailun
Relying on the Jinping Deep Earth Nuclear Astrophysical Experimental Device (JUNA for short), Chinese scientific researchers directly measured the breakthrough reaction cross-section of the key nuclear celestial reaction - fluorine radiation captured protons in 2021, pushing the measurement range to the world's lowest energy area and discovering a new resonance, explaining the origin of calcium abundance of the oldest known stars in the universe. This result supports the weak supernova explosion model of the first generation of stars, revealing the evolutionary fate of ancient stars. The papers related to were published in the journal Nature on October 26, Beijing time.
China Jinping Underground Laboratory Phase II Entrance. Photo by Zhang Gailun
In 2014, researchers observed a K-type red giant , and observed lithium, carbon, magnesium and calcium elements on the red giant, but no iron elements were observed, and it was called the extremely poor metal third star family. It is regarded as the oldest known star in the universe and was born about 100 million years after the Big Bang . To be precise, it is a ruin formed after the first generation of star supernova exploded . The celestial theory believes that its calcium may come from the breakthrough reaction of the thermal carbon, nitrogen and oxygen cycle, but data support is still needed.
paper first corresponding author and professor He Jianjun told Science and Technology Daily reporter on the 26th that calcium was born from some key nuclear reactions . The probability of thermonuclear reactions occurring under typical temperature environments of the first generation of stars (0.1GK, i.e. 100 million degrees Celsius) is extremely low, and direct measurement is very difficult. China Jinping Underground Laboratory is the deepest underground laboratory in the world. The cosmic ray flux can be reduced to one tens of millions to one billionth of the ground, which is conducive to the precise measurement and research of rare reaction events. JUNA is located in the second phase of the Jinping Underground Laboratory in China. It is led by Chinese Academy of Atomic Energy Sciences and has been completed and released by the end of 2020 with scientific research institutions such as the Institute of Modern Physics of the Chinese Academy of Sciences, Beijing Normal University, and Tsinghua University .
After several years of hard work, He Jianjun and his scientific research team have developed the fluorine injection target with the strongest resistance to radiation . The experiment was conducted with a strong current proton beam to bombard the fluorine target, and the gamma ray released after the collision was detected and analyzed, and the key nuclear reaction was directly measured. The strong current proton beam provided by the Kimpian accelerator successfully pushed the breakthrough reaction to the lowest energy point in the world and discovered a new resonance at 225 thousand electron volts. The calculation of the
model shows that the probability of the breakthrough reaction of breaking out from the carbon-nitrogen-oxygen cycle is about 7 times higher than previously expected, verifying the hypothesis that calcium originates from the breakthrough reaction. It also strongly supports the weak supernova explosion evolution model of the first generation of stars. means that a black hole is generated in the center after the explosion of the star. The lighter elements on the outer layer are thrown out, and the heavier elements on the inner layer are sucked into the black hole, which also explains why people have not observed the iron elements in the third star family.
As one of the first results, the successful development of breakthrough reaction experiments proves that JUNA has fully possessed the ability to conduct deep nuclear astrophysics research. Nature reviewers believe this is a huge experimental success, which provides new avenues for future nuclear astrophysics research.
Source: Science and Technology Daily
Column Editor: Qin Hong Text editor: Li Linwei Title picture source: Xinhua News Agency Picture editor: Su Wei
Title picture description: The picture shows the Jinping Mountain Tunnel, and the China Jinping Underground Laboratory is in the middle of this tunnel.
Source: Author: Science and Technology Daily
