Starry stream of the Phoenix rose from the ashes of ancient star cluster
Observations of the star system called a stellar stream of the Phoenix helped the scientists to determine the nature of star clusters with extremely low content of heavy elements. The results of the study will help to learn more about education and the duration of existence of the milky Way.
Globular clusters — one of the most mysterious objects in the Universe. It’s a system about 100 000 stars located in the region of 10 parsecs (a few dozen light years) in diameter and most of them are almost as old as the universe. Globular clusters revolve around the almost all known galaxies, which have more than a billion stars. Spheroidal distribution around these galaxies implies that many of them were formed in other low-mass galaxies, which once revolved around the Central galaxy, but have since been accretionary this galaxy and crushed her tidal (gravitational) forces.
Astrophysics learned to use globular clusters as “fossils” for the reconstruction of this process of accretion, which promotes the formation of large galaxies. However, globular clusters can also be destroyed by tidal forces of the galaxy-host.
Researchers monitored the poorest metal ball cluster. The chemical composition of stars in a globular cluster is a key observable feature, which connects them to their Natal galaxies. The stars in the cluster were born together in the same parental molecular gas cloud, and have a very similar chemical composition. More specifically, all the stars in the cluster have the same iron content, which in turn reflects the iron content of the galaxy in which they formed.
The researchers used spectroscopic observation of a shooting star flows South to measure metal content in 11 stars in the star stream of the Phoenix, a group of stars orbiting the galactic center at a distance of about 20 000 parsecs. Surprisingly, the researchers measured the extremely weak absorption lines of calcium (which is closely correlated with the iron content of the stars), the result was that these stars contain about 0.20 ± 0.03% of metal in comparison with the Sun. Moreover, the “metallicity” of stars uniformly low. This variation of the metal content is much lower than that of dwarf galaxies, which means that the flow of the Phoenix is not the rest of the system. Instead, it indicates that the stars in the stream Phoenix were born in the same star cluster.