A view of the Milky Way appears in the sky in the Uruguayan countryside. File / AFP

Mariecar Jara-Puyod, Senior Reporter

Astronomers have always been curious to know about the young and old stars that exist in the 13.1 billion-year-old Milky Way — the galaxy that houses the Earth and its solar system and appears as a whitish band in the clear summer night sky.

A team of astronomers of the European Union-funded “Asterochronometry” project had so far successfully studied and surveyed 100 of the 400 billion stars oscillating within the whitish band.

Interviewed, principal investigator Dr. Andrea Miglio said the 100 selected stars were “red giant branch stars (whose iron content is four to 50 times less than in the sun), which is a good indicator of an old population. The final sample contains only 95, with ages from two to 16 billion years.”

Gulf Today got in touch with Miglio of the University of Birmingham-School of Physics and Astronomy (UK), following the May 17, 2021 publication of the “Chronologically dating the early assembly of the Milky Way” in “Nature Astronomy.”

Miglio co-authored the research. Lead writer is his colleague, Dr. Josefina Montalban. 

Montalban said: “The chemical composition, location and motion of the stars we can observe today in the Milky Way contain precious information about their origin. As we increase our knowledge of how and when these stars were formed, we can start to better understand how the merger of the Gaia Enceladus, also known as the Gaia Sausage, occurred.”

Miglio is an active member of several space missions, one of which is the ongoing “Kepler” of the National Aeronautics and Space Administration (USA) which has been recording the brightness of 170,000 stars since 2009. He differentiated Milky Way from Gaia Enceladus: “(The former) is “our (massive) galaxy (much massive) than the mass of the sun at the centre of a group of galaxies. (The latter) is a “dwarf galaxy, a satellite of our own and more massive than the small Magellanic cloud, which entered the Milky Way’s gravitational field and merged with it.”

Asked on whether the Milky Way stars dating was highly necessary, Miglio said: “It is true that the number of galaxies in the universe is huge. I would not be able to answer the question of how many there are. The Milky Way is only one among many. However, it is the only one that allows us to study its  composition and structure in detail. Thanks to its common character. Studying it allows us to know also many others whose details are not accessible with such precision. The Milky Way Halo is largely made up of remnants of the numerous collisional or accretion events.