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Presumed young star turns out to be a galactic senior citizen by Staff Writers Bochum, Germany (SPX) Jan 18, 2017
49 Lib, a relatively bright star in the southern sky, is twelve billion years old rather than just 2.3 billion. For many decades, researchers were stumped by conflicting data pertaining to this celestial body, because they had estimated it as much younger than it really is. Determining its age anew, astronomers at Ruhr-Universitat Bochum (RUB) have now successfully resolved all inconsistencies. Dr Klaus Fuhrmann and Prof Dr Rolf Chini published their results in the Astrophysical Journal. "It had previously been assumed that the star was only half as old as our sun," says Chini. "However, our data have shown that it had been formed at the time that our galaxy was born." The reason for the error: the celestial object is a dual star system, as was proved by another research group in 2016. Chini's team has now demonstrated the mechanism used by the star partner of 49 Lib to fake its age.
Invisible star companion Scientists determine the age of stars based on their chemical composition. Old stars that had been formed during an early stage of the universe do not contain any heavy elements. This is because those elements were generated later, following the nuclear fusion of many generations of stars. Young stars such as our sun possess heavy elements, because they have emerged from the remnants of past generations of stars.
Giant at the close of its life At the end of their life, stars become huge; so huge that their own gravity is no longer sufficient to keep the matter together. The matter escapes as gas into space. Should there be another star in its vicinity, its gravity might attract and absorb the expelled matter. This is how 49 Lib gained its heavy elements.
Determining the age of stars Based on their data, the RUB researchers did more than just specify the age of the analysed star. "We are able to track this dual system's entire evolution," explains Rolf Chini. The astronomers know, for example, the masses with which the star's life had begun and how those masses have evolved since then.
From white dwarves to supernova As a red giant, 49 Lib will no longer be able to keep its matter together, undergoing the same process that its star partner underwent as it turned into a white dwarf. Part of the matter of 49 Lib will be attracted by its extinguishing star partner. "If that partner cannot rid itself of the matter in small eruptions, it will fully explode as a supernova," says Chini.
Related Links Ruhr-University Bochum Stellar Chemistry, The Universe And All Within It
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