Astrophysicists from the Federal Polytechnic School of Lausanne were actively involved in the discovery of a rare star - very old and with a low metal content. As a messenger from the distant past, she will help scientists learn more about the young universe.
“We have made a great discovery that challenges our understanding of the formation of the first generations of stars in the universe,” says Pascal Jablonca, a researcher at the Ecole Polytechnique de lausanne (EPFL).
Jablonka is one of the founders of the Pristine study. This is an international project dedicated to the search for the oldest stars with a low metal content. In the course of the project, an extremely rare object was discovered. The star found was named Pristine 221 and is one of the ten stars with the lowest metal content in the galactic halo. What's more, it is one of two unusual stars with almost no carbon. An article about the discovery was published in the Monthly Notices of the Royal Astronomical Society.
The Pristine team used a special narrow-band filter installed on the Canada-France-Hawaii Telescope (CFHT Telescope) to pre-select stars with an intact atmosphere. After that, a detailed spectroscopic campaign was carried out using the telescopes of the Group. Isaac Newton in Spain and the European Southern Observatory in Chile. EPFL researchers Pascal Jablonca and Carmela Lardot formed one of three teams, with the Paris Observatory and the Canary Institute of Astrophysics spearheading the spectroscopic analysis and chemical content measurements that led to the registration of this particular star. They were able to demonstrate that the star does indeed have few heavy elements in its atmosphere.
The spectrum of Pristine 221 shows many hydrogen lines and very few other elements besides a small volume of calcium. This indicates an extremely low metal content in the star. This unusual lack of heavier elements in its atmosphere means that it most likely belongs to an early generation of stars formed in the Galaxy / Ecole Polytechnique Federale de Lausanne.
“Most of the elements have indices from 10 thousand to 100 times lower compared to the Sun. In addition, the detailed structure of its various elements is highlighted. While stars with extremely low metal abundances usually have very high carbon values, this is not the case with this star. This makes it the second of its kind and an important messenger from the early universe,”says Else Starkenburg, a researcher at the American Institute of Physics and lead author of the study.
“Previously, scientists believed that carbon was a necessary cooling agent to help small fragmentation of the gas cloud from which stars were formed and to form low-mass stars in the cosmological redshift universe,” explains Pascal Jablonca. “With two representatives of these old low-carbon stars now, we have to rethink existing models.”
Vladimir Guillen
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