The PIGS team makes a sensational discovery in the center of the Milky Way

International researchers have carried out an impressive accounting of the oldest stars in the central part of the Milky Way. A group of scientists known as the Pristine Inner Galaxy Survey (PIGS) has found that these stars spin around the center of the Milky Way very slowly. Previously, it was thought that their location may be chaotic. It has also been found that these ancient stars spend a significant part of their long lives in close proximity to the center of the galaxy.

Artist’s impressions of ancient stars in the inner region of the Milky Way. Several examples of the orbits of stars are highlighted on the left. The right side shows the location of these stars in the galaxy of a relatively slowly spinning Sun. Authorship: ESA/Gaia

Some stars that appeared during the first billion years after the Big Bang are still preserved and can be used to study the conditions that prevailed in galaxies at the very beginning of their formation. They differ in their original chemical composition, mainly of hydrogen and helium, with a lower content of heavy elements compared to young stars such as the Sun. Astronomers usually search for these ancient stars in remote regions on the edge of the galaxy, where the low density of matter makes them easier to detect.

In theoretical models, it was assumed that the oldest stars should be present in the dense inner regions of the Milky Way. However, the search for these stars in this region is quite difficult, since the path to the center of the galaxy is almost completely blocked by interstellar dust, and ancient stars are extremely rare compared to their young neighbors.

The PIGS team used a special filter to process images captured on the CFHT telescope to effectively select potential stars. Confirmation was obtained through spectroscopic observations carried out on the Anglo-Australian AAT telescope, which allowed them to obtain the largest set of detailed observations of untouched stars in the inner part of the Galaxy.

The PIGS observations were combined with data from the Gaia space mission to study the movements of these ancient stars in the Milky Way. It turned out that the older the stars, the more chaotic their movements. But even the old found stars still show a certain average motion around the center of the Galaxy. In addition, many of these stars spend almost their entire long existence within the inner part of the Galaxy – inside the conditional sphere between the center of the Galaxy and the Sun.

According to

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