Astronomy: By far the most pristine star discovered in the Milky Way
The earlier a star formed in the universe, the fewer elements other than hydrogen and helium it contains. Now the most pristine found so far has been discovered.
Artistic representation of the star on its way from the Large Magellanic Cloud to the Milky Way
(Image: Navid Marvi/Carnegie Science)
A research group, including several students from the University of Chicago, has discovered the most chemically pristine star known to date. The university has now made this public, explaining that the celestial body, designated SDSS J0715−7334, consists almost exclusively of hydrogen and helium. The proportion of heavier elements is said to be only half that of the previous record holder, making it by far the oldest star discovered so far. The star is approximately 80,000 light-years away and originally comes from the outer region of the Large Magellanic Cloud, a dwarf galaxy in the immediate vicinity of the Milky Way.
Exciting Studies
As the research group recalls, the very first stars after the Big Bang could only consist of helium and hydrogen. They burned hot and died quickly. But heavier elements had formed in their cores, which were ejected into space during the final explosion. This made them available for the formation of the next generation of stars, and over time, the proportion of these heavier elements in the stars has increased. In astronomy, this is referred to as metallicity. The lower it is, the more pristine a star is, and SDSS J0715−7334 surpasses everything known so far, the group writes. The measurement data are presented in an article in the scientific journal Nature Astronomy.
The star was discovered by a group of students who were searching data from the SDSS (Sloan Digital Sky Survey) for stars with anomalies. The explicit goal was to identify stars that appear to have particularly low metallicity, the university writes. When they found a handful, the group traveled to the Magellan Telescopes in the Chilean mountains for more precise analyses. Already on the first night, there were signs that they had found something very special. This was quickly confirmed, and in the following months, the group was busy analyzing the data and writing the research paper.
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The discovery of SDSS J0715−7334 can therefore also answer the question of why stars have become smaller with increasing generations. Previously, it could not be determined whether this was due to the growing proportion of heavier elements or cosmic dust. However, the star discovered now does not consist of enough heavier elements to explain the smaller size. This suggests that cosmic dust (solid particles such as soot or silicates) is responsible for the successive generations of stars shrinking. This can now be further investigated. Furthermore, the finding presented now is intended to help discover more such stars. The students, however, are already speaking of an "incredible" experience.
(mho)
