Motherboard reports:

Scientists have opened an unprecedented window into the universe’s very first stars by conducting nuclear fusion experiments in a subterranean laboratory located 1.5 miles under China’s Jinping Mountains, reports a new study.

The results resolve a longstanding mystery about one of the oldest stars ever discovered, while also shedding new light on the murky reactions that powered the ancestors of all modern stars.

One of the biggest quests in astronomy is to directly observe the first stars that ever shone in the cosmos, known as “population III.” Scientists think this initial generation of stars burst into existence somewhere around 100 to 250 million years after the Big Bang, before quickly burning out and exploding as enormous supernovae.

Population III stars have never been seen by humans, but scientists have spotted stars that were born from the ashes of these stellar elders. One such star, called SMSS0313-6708, has been shining for an astonishing 13.6 billion years, making it one the oldest stars ever spotted. Located just 6,000 light years from Earth, the ancient star has puzzled scientists because it contains a higher concentration of the element calcium than expected for a star from the early universe.

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

Zhang and colleagues discovered that a particular reaction, which produces a version of the element neon, could be 7.4 times more common in population III stars compared to previous estimates. The finding explains the high calcium content of SMSS0313-6708 and provides an updated measurement of this “crucial reaction” that has been “previously inaccessible in aboveground laboratories,” according to a study published on Wednesday in Nature. [Continue reading…]