The oldest stars in the universe were giants that burned rapidly and died young in spectacular explosions. They may never be directly visible, but NASA’s James Webb Space Telescope may be lucky if it can spot when they shine when viewed from a distance. Meanwhile, astronomers may have discovered the next best thing: a baby born from the debris of a first-generation star that has been glowing quietly near the Milky Way ever since. A closer look and the discovery of more such lineages could tell researchers how massive the first stars were and how they influenced the evolution of the universe.

“We’re trying to do a forensic analysis of objects that exploded 13.5 billion years ago. They’re not there anymore,” says astronomer Timothy Beers of the University of Notre Dame, who was not involved in the study. “If it’s clean [нащадок]This places very strong constraints on the masses of the first stars.

Theorists believe that the first generation of stars, known as Population III, consisted only of components left over from the Big Bang, mostly hydrogen and helium. As they burned, they broke these materials down into heavier elements, which astronomers grouped as “metals.” When stars exploded as supernovae after several million years of existence, the metals spread into subsequent generations of stars and mixed with hydrogen and helium.

The limited content of the population of III stars is thought to be the reason why they have grown so large. For a gas cloud to turn into a star, the gas must cool. Metals efficiently convert heat into infrared light, which can escape from the cloud. Without them, III. The population of stars grew larger and larger until gravity overcame the hot gas and initiated a thermonuclear burn in the core.

Views differ on how large they are, although model predictions range from a few tens of times the mass of the Sun to 1,000 times its mass. Determining the size is important because at that time something hot and bright ionized almost all of the neutral gas permeating the universe. A huge population of tertiary stars could be a possible cause, while smaller ones are less so.

Although observers can never directly measure the size of a Population III star, they can detect the signatures left behind when stars die in a rare form of explosion called a “binary instability” supernova, which occurs when stars are 140 to 260 times larger. than the sun. In such a star, the superheated core emits gamma rays, which exert external pressure and support the star’s outer layers. However, if the energy of gamma rays gets too high, the rays can turn into electron-positron pairs and stop applying pressure. Without this pressure, the outer layers would collapse, causing a fusion reaction that would tear the star apart. Models suggest that double-instability supernovae create a special structure of excess metal that can then be used by future generations of stars.

This pattern will emerge in the new star’s elemental composition, like a fingerprint that astronomers can read in the star’s light spectrum. For decades, they looked for these signatures in large surveys that regularly recorded the spectra of millions of objects in the sky. But the search for signs of supernova binary instability has been disappointing. In one such initiative, a team led by the University of Florence announced earlier this year that it had found 166 candidate population III lineages after analyzing the spectra of 1.4 million stars in the Milky Way. But when a more detailed spectrum was taken, neither made the cut. “I began to doubt whether these stars even existed,” says Ioanna Coutsuridou, an astronomer at the University of Florence.

But in June, researchers from another team showed they had hit the jackpot using China’s Large Sky Field Multi-Object Fiber Optic Spectroscopic Telescope (LAMOST). They found the star, known as J1010+2358, in the rare halo of stars surrounding the Milky Way that is surprisingly low in metal. For the individual metals the team was able to detect, the star also showed significantly different abundances of elements with odd and even atomic numbers; this is indicative of a double unstable supernova. “It was a perfect fit,” says Kutsuridu.

Last week, he and his colleagues took the LAMOST team’s analysis a step further in a preprint published on arXiv. They compared the metal content of J1010+2358 to different models of Population III stars and supernovae. They concluded that this was probably the generation of a star with a mass between 250 and 260 solar masses, indicating a bias in the class III population in favor of intermediate-mass stars. But it is not yet clear whether its predecessor is typical or exceptional. Koutsuridu and his team hope to rectify this by using other telescopes to measure metals missing from the LAMOST survey.

J1010+2358 is just an example. To truly determine the nature of Population III stars, astronomers need to find more stars of this type, Beers says. “They are the biggest stars,” he says, but watching them “has always been difficult.”