Scientists conduct nuclear fusion tests deep in a mountain, discovering the secrets of the first stars

Scientists conduct nuclear fusion tests deep in a mountain, discovering the secrets of the first stars

Jinping underground laboratory. Photo: Xinhua via Getty Images


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Scientists have opened an unprecedented window into the universe’s first stars by performing nuclear fusion experiments in an underground laboratory located 1.5 miles under China’s Jinping Mountains, according to a new study.

The findings solve an ancient mystery related to one of the oldest stars ever discovered, while also shedding new light on the mysterious interactions that supported the ancestors of all modern stars.

One of the biggest tasks in astronomy is Observe the first stars directly That shone in the universe, known as “Population 3”. Scientists believe that this initial generation of stars exploded into existence somewhere around 100 to 250 million years after the Big Bang, before quickly fading out and exploding as massive supernovae.

Humans have not seen the stars of the third group before, but scientists have spotted them Stars born from ashes One of these elders is the stars. One of these stars, called SMSS0313-6708, was shining 13.6 billion years ago, making it one of the oldest stars ever observed. Located only 6,000 light-years from Earth, the ancient star has baffled scientists because it contains a higher concentration of the element calcium than would be expected for a star from the early universe.

Now, scientists led by Liyong Zhang, a researcher at Beijing Normal University, have re-established an important nuclear reaction that facilitates the production of heavy elements, such as calcium, in ancient stars. The team conducted the experiment inside the China Jinping Underground Laboratory (CJPL), an underground tunnel located under 2,400 meters of vertical rock, the world’s deepest operational laboratory for particle and nuclear physics experiments.

Zhang and his colleagues discovered that a specific reaction, which results in a version of the element neon, could be 7.4 times more common in the third group of stars than previous estimates. The results explain the high calcium content of SMSS0313-6708 and provide an up-to-date measure of this “critical interaction” that was “previously inaccessible in aboveground laboratories,” according to the A study published on Wednesday in temper nature.

“Stars are the nuclear formations of the universe, and they are responsible for the formation of most of the elements heavier than helium in the universe,” Zhang’s team said in the study. “Some of these elements are created in the cores of stars over billions of years, while others are formed in just a few seconds during the explosive death of massive stars.”

“These heavy elements play an important role in the universe, enabling the formation of complex molecules and dust, facilitating the cooling and condensation of molecular clouds, which helps form new stars like our sun,” the researchers continued. “The first generation of stars, called Population III (pop III) stars or primordial stars, consists of the original matter left over from the Big Bang, and therefore plays a special role in supplying the universe with the first heavy elements and creating the conditions for future generations of stars and galaxies.”

In other words, each new generation of stars is enriched with the heavy metals produced by its predecessors, and then pushes the cycle forward by implanting the universe with a new set of complex heavy elements. Group C stars were made almost entirely of the light elements, hydrogen and helium, but their explosive deaths created heavier elements that were incorporated into stars such as SMSS0313-6708.

Zhang’s team noted, “SMSS0313-6708 is a very metal-poor star believed to be a direct descendant of the first generation of stars in the universe that formed after the Big Bang.” “The observable composition of the super-poor star is a time capsule of the environment before the first galaxies formed – complementing the exciting upcoming observations of the James Webb Space Telescope, which is now aimed at getting a first look at the first stars and galaxies.”

The scientists’ current task was to take advantage of the laboratory’s subterranean location – which protects it from cosmic radiation that reaches Earth and is disrupted by precise instruments – to discover nuclear fusion reactions.

Previous studies identified fluorine-19, an isotope (or version) of the light element fluorine, as an important component in the interiors of older stars. When fluorine-19 hits a proton, a type of subatomic particle, it can undergo two types of reactions that have very different effects on the production of chemicals within these star formations. One reaction produces the oxygen isotope, while the other produces the isotope neon-20 and gamma rays. The first reaction essentially causes regeneration to produce lighter elements, while the reaction that makes Neon 20 causes a “breakout” mechanism that enables stars to form heavier elements.

Most studies have suggested that the penetration reaction is about 4,000 times weaker than the oxygen reaction in connection with the production of elements in stars, a process called nucleosynthesis. Zhang’s team was able to test this idea experimentally in the unique conditions of CJPL, by firing protons at fluorine-19 without annoying perturbations from natural radiation. The results showed that the penetration reactions were much stronger than expected, and could explain the calcium content seen in SMSS0313-67086.

“Our stellar models show a stronger eruption during stellar hydrogen combustion than previously thought, and may reveal the nature of calcium production in Group C stars imprinted on the oldest known super-poor star, SMSS0313-67086,” the team said. “Our rate shows the effect that faint Group III stellar supernovae can have on the nuclear structure observed in the oldest known stars and first galaxies, which are prime targets for the James Webb Space Telescope mission.”

“We found that all of our nucleosynthesis models can reproduce the observed calcium production,” the research added.

In this way, experiments conducted in the depths of the Earth revealed the mysterious mechanisms that control the production of elements in the depths of stars, including the third generation of the mysterious inhabitants. As Chang’s team notes, sophisticated observatories, including the James Webb Space Telescope, will add more detail to this emerging picture of stellar interiors — and possibly reveal the first sky-lighting starlight in the early universe.

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