Tuesday, February 27

Chemists Track Disappeared Massive Stars 2023

On the fringes of the Milky Way Galaxy, astronomers have discovered a star with a chemical composition unlike anything they have ever seen. It corresponds to the chemical traces left behind by very massive, very early stars, as predicted by theory.

This is the most convincing evidence to date that the first stars were colossal stars. Models indicate that such stars would not have left any other traces, so this is the best evidence that can be hoped for.

It is believed that the first generation of stars in the universe included stars hundreds of times more massive than the Sun. A star of this size would have exploded after a brief existence, leaving no remnants for astronomers to investigate.

Scientists Use Chemical Signatures to Pinpoint Massive Stars That Have Disappeared

The gas emitted by the explosions of these very first, extremely massive stars would have had a distinct chemical signature than the gas emitted by the explosions of less massive, longer-lived stars. This gas is incorporated into the stars of the next generation.

Therefore, a second-generation star with the chemical signature of a first-generation predecessor could provide us with information about the first stars in the universe. However, subsequent supernovae will trample the imprints of the first stars. Astronomers are therefore searching for the earliest remaining stars in an effort to locate a distinct, uncontaminated trace of the first-generation stars.

A group of astronomers from the National Astronomical Observatory of Japan (NAOJ), the National Astronomical Observatories of China (NAOC), and other institutions utilized the Chinese survey telescope LAMOST to identify the oldest stars in the Milky Way Galaxy and the NAOJ’s Subaru Telescope to measure their chemical compositions.

Among them, the team discovered LAMOST J1010+2358, which has a chemical composition consistent with that of stars of the first generation. This is the clearest trace of extremely massive first-generation stars ever discovered, and it provides significant support for the theory that stars with masses greater than 140 times that of the Sun formed in the early universe.

The results were published in Nature on June 7, 2023 as “A metal-poor star with abundances from a pair-instability supernova” by Qian-Fan Xing et al.

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