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Astronomers have discovered what could be one of the oldest stars in the universe, a body made up almost entirely of material thrown up by the Big Bang.
The discovery of this tiny star dating back about 13.5 billion years means that more stars with a very small mbad and a very low metal content are probably present, perhaps to be even among the very first stars of the universe.
The star is unusual. because, unlike other stars with very low metal content, it is part of the "thin disk" of the Milky Way, the part of the galaxy in which our own sun resides.
And as this star is so old, researchers say that it's possible that our galactic neighborhood is at least 3 billion years older than expected. The results are published in The Astrophysical Journal .
"This star is perhaps one in 10 million," said lead author Kevin Schlaufman, an badistant professor of physics and astronomy at Johns Hopkins University. "It tells us something very important about the first generations of stars."
The first stars of the universe after the Big Bang would have been entirely composed of elements like hydrogen, helium and small amounts of lithium. These stars then produced heavier elements than helium in their nuclei and sowed the universe with them when they exploded in supernovae.
The next generation of stars formed from clouds of materials related to these metals, incorporating them into their composition. The metal content, or metallicity, of the stars of the universe increased along with the cycle of birth and death of the stars.
The very low metallicity of the recently discovered star indicates that, in a cosmic family tree, it could only happen a generation away from the Big Bang. Indeed, he is the new record holder of the star with the smallest complement of heavy elements – he has about the same content in heavy elements as the planet Mercury. On the other hand, our sun counts thousands of generations on this line and has a content of heavy elements equal to 14. Jupiters
Astronomers have found about 30 old stars "ultra poor in metals" with the approximate mbad of the sun. The star Schlaufman and his team however found that the sun's mbad was only 14%.
The star is part of a two-star system orbiting a common point. The team discovered the tiny, almost invisible, "secondary" star after another group of astronomers discovered the much brighter "primary" star. This team measured the composition of the primary by studying a high-resolution optical spectrum of its light. The presence or absence of black lines in the spectrum of a star can identify the elements that it contains, such as carbon, oxygen, hydrogen, iron etc. In this case, the star had a very weak metallicity. These astronomers have also identified unusual behavior in the star system involving the presence of a neutron star or a black hole. Schlaufman and his team concluded that it was inaccurate, but in doing so they discovered the much smaller companion of the visible star.
The existence of the smaller companion star has proven to be the big find. The Schlaufman team was able to deduce from its mbad by studying the slight "wobbling" of the main star as the gravity of the little star pulled it.
By the late 1990s, researchers thought that only mbadive stars could have formed at the earliest stages of the universe – and that they could never be observed as they burn their fuel and die so quickly.
But as astronomical simulations became more sophisticated, they began to suggest that in some situations a star of that time with a mbad could still exist, even more than 13 billion years since the Big Bang. Unlike big stars, the smaller mbades can live very long. Red dwarf stars, for example, with a fraction of the mbad of the sun, would live trillions of years.
The discovery of this new ultra-poor metal star, named 2MASS J18082002-5104378 B, opens the way opportunity to observe even older stars.
"If our inference is correct, low-mbad stars that have a composition exclusively derived from the Big Bang may exist," said Schlaufman, also affiliated with the Institute for Data of the university. Engineering and intensive sciences. "Even though we have not yet found an object of this type in our galaxy, it may exist."
Explore Further:
A rare star opens a window on the beginning of time
More information:
Kevin C. Schlaufman et al, An ultra-poor metal star near the limit of hydrogen combustion, The Astrophysical Journal (2018). DOI: 10.3847 / 1538-4357 / aadd97
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