Chinese researchers have deeply experimented to reveal the mystery of the origin of calcium in ancient stars.

Chinese researchers have revealed the mystery of the origin of calcium in the oldest known star in the universe through deep experiments. Recently, related papers were published in the international journal Nature.

In 2014, Australian astronomers used telescopes to observe the oldest red giant in the universe. It was born about 100 million years after the Big Bang and consisted of a nebula formed by the supernova explosion of the first generation of stars. At that time, lithium, carbon, magnesium and calcium were observed, and the origin of calcium has always been a mystery.

Celestial theory holds that its calcium element may come from the breakthrough reaction of thermal carbon, nitrogen and oxygen cycle, but there is no experimental data to support it, which makes it difficult for the current stellar evolution model to explain astronomical observation data. He Jianjun, the first correspondent and professor of Beijing Normal University, said that the probability of thermonuclear reaction in the first generation of stars is extremely low. Due to the interference of cosmic ray background, people have been unable to directly measure these reactions in the ground laboratory. Jinping Underground Laboratory in China is the deepest underground laboratory in the world at present, with a vertical rock coverage of 2,400 meters, which can reduce the cosmic ray flux to one ten thousandth to one hundred millionth of the ground level.

△ Explore the mysteries of the universe in the deepest laboratory in the world, Jinping Underground Laboratory in China.

The Jinping Deep-Earth Nuclear Astrophysics Device, led by Liu Weiping, a researcher from China Academy of Atomic Energy, was built in the deep by the end of 2020 in collaboration with the Institute of Modern Physics of Chinese Academy of Sciences, Beijing Normal University, Tsinghua University and Yalong River Basin Hydropower Development Co., Ltd.. After several years of preparation and research, the team of Professor He Jianjun from the School of Nuclear Science and Technology of Beijing Normal University carried out the direct measurement experiment of fluorine-captured protons with this device. Finally, the hypothesis that calcium comes from the breakthrough reaction of carbon, nitrogen and oxygen cycle is verified, and the origin of calcium in ancient stars is successfully explained, which strongly supports the weak supernova explosion evolution model of the first generation of stars and will provide reliable data for future observation of james webb telescope.

The reviewers of Nature think that this is a great experimental success, which provides a new way for future nuclear astrophysics research. The results of this research will arouse strong interest in nuclear astrophysics, including experimental physics, star modeling and observation.

(CCTV reporter Xu Wei Wang Xinqi)