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Chemical traces offer evidence of the universe's earliest stars

First-generation stars had short lives that ended in partial explosions and can be detected only through the chemical signatures they left in the stars that succeeded them.
The stars of the Milky Way over Montana's Paradise Valley.
The stars of the Milky Way over Montana's Paradise Valley.Ray Farmer / NBC News

HONG KONG — An international research team has found the first chemical traces of some of the oldest stars in the universe.

The study by researchers from China, Australia and Japan, which was published online in the journal Nature last week, confirmed the existence of massive stars in the early universe.

“Astronomers had speculated that in the early universe, there were stars that could be extremely colossal,” Zhao Gang, a researcher from the National Astronomical Observatories, Chinese Academy of Sciences and one of the study’s authors, told NBC News. “Scientists had been trying to find the proof for decades.”

Zhao and his team found that so-called first-generation stars, which lit up the universe as early as 100 million years after the Big Bang, could have had a mass as much as 260 times that of the sun, which matched the predictions of astronomers.

First-generation stars had short lives that ended in partial explosions and can be detected only through the chemical signatures they left in the generation of stars that succeeded them. Those first-generation stars could become parent stars to the later-generation stars that bequeath their chemical signatures.

Meanwhile, the first-generation stars were made almost entirely of hydrogen and helium, while current stars contain more metal elements. Thus, researchers were looking for stars without many metal elements.

The researchers focused on a star named LAMOST J1010+2358, which has particular chemical characteristics. After researchers matched its chemical spectrum with the theoretical models, they confirmed that the parent star of LAMOST J1010+2358, the first-generation star, had 260 times the mass of the sun.

“The first-generation star we observed has the potential to become the oldest star we have ever seen,” said Alexander Heger, a professor in the school of physics and astronomy at Monash University in Australia who was part of the research team. “It probably had only lived for 2 1/2 million years and then exploded.”

Heger added that it was important to investigate first-generation stars because “this is how it all begins.”

“It’s about understanding our origins and the origins of the universe,” he said. “So far, this is sort of a blind spot in our understanding of the entire history of the universe.”

Quentin Andrew Parker, director of the Laboratory for Space Research at the University of Hong Kong, said this kind of evidence was extremely difficult to find.

“It’s like looking for a needle in a haystack because our galaxy is made up of billions and billions of stars,” said Parker, who was not involved in the research.

The findings were based on observations from two of the largest land-based telescopes in the world, the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) near Beijing and the Subaru Telescope in Hawaii, which is operated by the National Astronomical Observatory of Japan.

“LAMOST has proved to be extremely efficient, taking spectra for vast numbers of stars,” Parker said. “You can take 4,000 spectra of 4,000 different objects at the same time.”

Parker said the research team’s success was not only a matter of fundamental science but also a result of “wonderful international collaboration,” citing the use of two telescopes operated by two nations and the talents of different researchers.

“If you just work in your silos and a nation here and you’re not allowed to collaborate with people around the world, then you don’t get the full picture,” he said. “You don’t have the right expertise. You don’t have the right insights.”

“That’s how modern science works at its best.”