They discover a stellar structure from the early stages of the Milky Way

A team of researchers discovered a stellar structure from the early stages of the Milky Way, reports this Wednesday the Spanish Institute of Astrophysics of the Canary Islands (IAC), which, in a statement, explains that it is the oldest globular cluster remnant found to date.

A discovery that was published this Wednesday in the magazine Nature, and in which data from the Gaia satellite of the THAT with observations made at the Gran Telescopio Canarias, installed at the Roque de los Muchachos Observatory (Spanish island of La Palma), together with the CHFT and Gemini-North telescopes at the Mauna Kea Observatory (Hawaii).

The globular clusters They are groupings of stars, generally very old, found on the margins of galaxies, and in the case of the one discovered in this investigation, the stars have an exceptionally low content of heavy elements.

This discovery “Opens a direct and unique window to the earliest times of star formation in the universe”, Says in a statement Nicolas Martin, a researcher at the Strasbourg Observatory, who is leading this work, and who adds that what was found is a relic from the time when the first stellar structures were created.

Until now, globular clusters with so few elements were not known to exist, making this a key discovery for understanding how stars formed in the early Universe.

To study the first stellar structures that were formed in the Universe, astronomers can look at the most distant galaxies, or study the oldest structures in the Milky Way in great detail, a methodology called “Galactic archeology”.

The vast majority of stars “that surround us, like the Sun, were formed in our galaxy. However, a small fraction of the Milky Way’s stars and clusters, which are found in its surroundings, were brought in from smaller galaxies ”, explains Jonay González, researcher at the Instituto de Astrofísica de Canarias and co-author of the article.

The discovered cluster was possibly introduced in this way, but it was losing its stars in its orbit around the galaxy as a result of tidal stresses, leaving a “Celestial footprint of stars”, Add.

This finding was possible thanks to the data taken by the mission of the Gaia satellite of the European Space Agency (ESA) and the identification of primitive stars by the Pristine Survey, which is being carried out at the Canada-France-Hawaii Telescope (CFHT), on Mauna Kea.

The team of researchers explored the map recorded by the Gaia satellite, using a novel algorithm to isolate these rare groupings of stars.

One of the structures discovered was a new stellar stream, which the team dubbed “C-19.”

In parallel, the Pristine study, from Hawaii, mapped the sky to systematically measure the percentage of heavy elements in millions of stars, and the combination of these two studies revealed that C-19 contains stars with an extremely low fraction of heavy elements.

Follow-up observations with the Gemini North Telescope, in Hawaii, and the Gran Telescopio Canarias (GTC or Grantecan), in La Palma, confirmed the globular cluster nature of the disturbed object, as well as the exceptionally low levels of heavy elements: so low as 0.04% of those of the Sun and far below any other known structure in the Universe.

The observations in the Grantecan They were key in confirming this primitive structure, identified by combining the maps of the Gaia mission and with observations in other telescopes on the ground, comments Carlos Allende, IAC researcher and co-author of the article.

The team of researchers for this work has the contribution of researcher Guillaume Thomas, from the IAC.