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A tiny star located about 1,590 light years from Earth could be as old as 13.53 billion years ago, making it one of the oldest stars ever discovered.
The tiny "ultra-low-metal" star called 2MASS J18082002-5104378 B – hereafter abbreviated J1808-5104 – and was discovered by an astronomical team led by Kevin C. Schlaufman of Johns Hopkins University. With an estimated age of 13.53 billion years, it is part of the first generation of stars to appear after the Big Bang, 13.7 billion years ago. It is not only one of the oldest stars of the Milky Way, but also one of the oldest stars in the universe. The details of this discovery are expected to be published in an upcoming edition of the Astrophysical Journal, but a pre-print has been published on arXiv.
"This star is perhaps one in 10 million," Schlaufman said in a statement. "It tells us something very important about the first generations of stars."
Indeed, the discovery challenges preconceived ideas about the nature and location of the first stars.
The first generation of stars to appear after the Big Bang was composed exclusively of elements like hydrogen, helium and traces of lithium. When these primordial stars exploded as supernovae, they covered the cosmos with heavier elements that were incorporated into the next generation of stars. Thus, the metal content, or metallicity, of the stars increased as the cycle of death and birth continued over the centuries.
Scientists spot one of the oldest stars of the Milky Way
Answer J0815 + 4729. If it was a Pokémon, it would be a bit like the Milky Way Level 3 Rattata.
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To date, astronomers have detected thirty or so old stars, low in metals, which tend to be as massive as our Sun. But J1808-5104 represents only 14% of the mass of our Sun, which led Schlaufman and his colleagues to assume that it was a red dwarf.
The recently discovered star, analyzed by astronomers with the Magellan Clay Telescope, the Las Campanas Observatory and the Gemini Observatory, is exceptionally low in metals. And in fact, it contains the smallest amount of heavy elements ever observed in a star, having roughly the same heavy element content as the Mercury planet. The amount of heavy elements in J1808-5104 is so small that researchers claim that it could only be a generation of the Big Bang. Before the new discovery, the Caffau star was considered the poorest star in metals, a star barely smaller than our Sun.
Stars the size of our Sun live about 10 billion years ago, but low-mass stars like this could theoretically burn billions of years.
"Reducing stars like these tend to shine very long," Schlaufman said. "This star has aged well. It looks exactly the same today as when it was formed 13.5 billion years ago. "
The location of this star in the Milky Way is also strange; J1808-5104 is part of the "thin disk" of the galaxy, where is also our Sun. The old, metal-poor stars are not supposed to be here, an active, overcrowded area that contains much younger stars. The discovery suggests that the slim disk of the Milky Way is about 3 billion years older than expected.
J1808-5104 is the smallest member of a two-star system. By measuring the "wobbling" of the largest star, caused by the gravitational influence of the smallest star, astronomers were able to deduce the mass of J1808-5104. High resolution optical spectroscopy has been used to identify elements such as carbon, oxygen, iron, and so on.
The new discovery is fascinating, but the results are strange and unexpected. This research should be replicated by other astronomers to ensure that Schlaufman and his team have not made any mistakes. That said, the discovery of J1808-5104 suggests even older stars of the Milky Way. As more ancient stars are discovered, we will learn more about the Universe during its very first period.
[The Astrophysical Journal]Source link
