The very first stars in the Universe might have been hundreds of times more massive than the Sun.
Astronomers have found evidence for the existence of the monster stars long thought to have populated the early Universe. Weighing in at hundreds of times the mass of the Sun, such stars would have been the first to fuse primordial hydrogen and helium into heavier elements, leaving behind a chemical signature that the researchers have now found in an ancient, second-generation star.
Little is known about the Universe’s first stars, which would have formed out of clouds of hydrogen, helium and a tiny amount of lithium in the first few hundred million years after the Big Bang.
Simulations have long predicted that some of this first batch of stars were enormous. With masses of more than 100 times that of the Sun, they would have lived and died in the cosmic blink of an eye, a few million years. As they exploded in supernovae, they created the first heavy elements from which later galaxies and stars evolved. But no traces of their existence have previously been found.
Now, using a technique called stellar archaeology, Wako Aoki at the National Astronomical Observatory of Japan in Tokyo and his colleagues have found the first hint of such a star, preserved in the chemical make-up of its ancient daughter. The chemistry of this relic — a star called SDSS J0018-0939 — suggests that it may have formed from a cloud of gas seeded with material created in the explosion of a single, very massive star. The results were published in Science on 21 August.
“This is a much awaited discovery,” says Naoki Yoshida, an astrophysicist at the University of Tokyo who was not involved in the study. That such chemical signatures have never been found in the Universe, despite many theoretical studies predicting their existence, is a long-standing puzzle, he says. “It seems Aoki et al. have finally found an old relic that shows intriguing evidence that there really was such a monstrous star in the distant past.”