Astronomers have found the ancient stars of the “embryo” of the Milky Way

(ORDO NEWS) — At the center of our Galaxy, a population of incredibly old stars has been identified – a cluster that appeared more than 12 billion years ago, becoming the “embryo” of the future Milky Way.

The center of our galaxy is in the constellation Sagittarius. There is a supermassive black hole, dense gas and dust clouds and many stars that are born and die especially quickly in this turbulent region.

But, in addition to them, there are also extremely old stars, which were once part of the protogalaxy, around which the entire vast Milky Way gathered.

Observations by the Gaia telescope helped to identify these stars and estimate the size of the “embryo” of our Galaxy.

The international team of astronomers was led by Hans-Walter Rix of the German Institute for Astronomy of the Max Planck Society. They used data from the DR3 survey conducted by the Gaia space telescope.

This astrometric tool is designed to collect the most accurate information about the positions, movements and spectra of stars and compile a detailed map of the Milky Way.

The telescope has collected information on more than a billion stars, but this time scientists have considered only those of them that are near the galactic center, within 30 angular degrees. About two million stars fell within these boundaries.

Of these, astronomers selected stars that have extremely low metallicity – less than three percent of the metallicity of the Sun.

This indicator reflects the content in the star of elements heavier than hydrogen and helium – those that were once formed in the depths of other luminaries and became part of the stars of new generations.

Low metallicity is characteristic of old stars. In addition, scientists have weeded out those of them whose movements do not allow us to connect them with the center of the Galaxy.

As a result, they identified 18 thousand stars that can be attributed to the remains of the “embryo” – protogalaxy.

These are exceptionally old stars, whose age can exceed 12.5 billion years. They still form a fairly compact cluster, and their movements reflect the initial set of rotation of the growing Galaxy.

The most ancient stars of this group practically do not move around the center, but the younger the star, the faster it rotates.

Gaia was not able to see all of them, many remained hidden behind the clouds. But if we approximate the total number of such stars, then their mass reaches 50-200 million solar masses.

This is about 0.2 percent of the total mass of the modern Milky Way, which “grew” around the protogalaxy over billions of years.


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