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article imageAstronomers find a 13 billlion-year-old star that shouldn't exist

By Andrew Moran     Aug 31, 2011 in Science
Heidelberg - Astronomers have discovered a 13 billion-year-old star located in the constellation Leo that shouldn't exist. Scientists explain that the star consists entirely of helium and hydrogen and is in the "forbidden zone" of star formation.
A star is created out of a cloud of cool, dense molecular gas, which then needs to collapse and increase in density in order for it to become a star. This occurs when the cloud collides with another cloud or if it encounters a giant supernova.
French and German scientists have stumbled upon a star that should have never existed in the first place, according to a news release. Utilizing the European Space Observatory's Very Large Telescope (VLT) and its X-shooter, the astronomers found that SDSS J102915+172927 is made up of helium and hydrogen.
The star has a mass 200 million times smaller than our Sun, is approximately 13 billion years old and is located in the constellation Leo of our Milky Way galaxy. Upon analysis of the star’s properties, it was concluded that it contains various chemical elements, but it also had a paucity of lithium.
The lack of lithium is surprising because a star that old would contain numerous elements, but the proportion of lithium was 50 times less than expected. SDSS J102915+172927 should have also contained a few more metals in it.
“A widely accepted theory predicts that stars like this, with low mass and extremely low quantities of metals, shouldn't exist because the clouds of material from which they formed could never have condensed,” said lead author of the paper, Elisabetta Caffau of Heidelberg University in German.
“It was surprising to find, for the first time, a star in this 'forbidden zone', and it means we may have to revisit some of the star formation models.”
Caffau added that the unusual star is not unique because astronomers have detected several more stars that should have possibly never existed. “We are now planning to observe them with the VLT to see if this is the case.”
Scientists have surmised that helium, hydrogen and lithium were created shortly following the Big Bang.
Results of this discovery will be published in the Sept. 1 issue of Nature.
More about Zentrum fur Astronomie der Universitat Heidelberg, constellation leo, Star, xshooter, uves instrument
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