98.5% of the Sun is made up of two light chemical elements, hydrogen and helium, while the remaining 1.5% consists of other heavier elements such as carbon, oxygen, and iron. The abundance of these heavier elements in a star is called its ‘metallicity’, and varies from star to star. It now turns out that our Galaxy is home to a stellar structure uniquely made of stars with extremely low metallicity, with a heavy element content 2,500 times lower than that of the Sun. This is well below that of any other known stellar structure in the Universe.
This discovery, made by an international team led by a CNRS researcher at the Strasbourg Astronomical Observatory (CNRS / University of Strasbourg), and involving scientists from the Galaxies, Stars, Physics and Instrumentation Laboratory (Paris Observatory – PSL / CNRS) and at the J-L Lagrange Laboratory (CNRS / Côte d’Azur Observatory), is published on January 5, 2022, in the journal Nature.
This group of stars all belong to a stellar structure in the Ruins of Ancient Star Cluster Discovered at the Fringes of Our Galaxy.
Reference: “A stellar stream remnant of a globular cluster below the metallicity floor” by Nicolas F. Martin, Kim A. Venn, David S. Aguado, Else Starkenburg, Jonay I. González Hernández, Rodrigo A. Ibata, Piercarlo Bonifacio, Elisabetta Caffau, Federico Sestito, Anke Arentsen, Carlos Allende Prieto, Raymond G. Carlberg, Sébastien Fabbro, Morgan Fouesneau, Vanessa Hill, Pascale Jablonka, Georges Kordopatis, Carmela Lardo, Khyati Malhan, Lyudmila I. Mashonkina, Alan W. McConnachie, Julio F. Navarro, Rubén Sánchez-Janssen, Guillaume F. Thomas, Zhen Yuan and Alessio Mucciarelli, 5 January 2022, Nature.
This work was carried out as part of the Pristine survey, with ESA’s Gaia space observatory, the Canada-France-Hawaii Telescope (Hawaii), the Gemini North telescope (Hawaii) and the GTC telescope (Canary Islands).