Astronomers accidentally found a globular cluster in the closest spiral galaxy to us, the Andromeda Nebula, in which the content of elements heavier than hydrogen and helium is about 800 times less than that of the Sun. This does not agree well with theories of the formation of such objects and galaxies, which requires their revision.. Article published in the journal Nature Globular clusters are dense gravitationally bound systems containing tens and hundreds of thousands of stars and are found in all large galaxies. There are several hundred of them in the Milky Way, and the age of these objects is comparable to the age of the Milky Way, which allows them to study the early stages of formation and evolution of galaxies, in particular to impose restrictions on the content of chemical elements in galaxies in the early Universe. The nearest spiral galaxy M31 (or the Andromeda Nebula) also has a system of several hundred globular clusters, which spatially and kinematically coincide with the stars in the outer parts of the galaxy and are divided into two subgroups.

A group of astronomers led by Soren Larsen from the University of Nijmegen reported the results of observations of the globular cluster RBC EXT8 in the galaxy M31, which is characterized by extremely low levels of metals (elements heavier than hydrogen and helium). The discovery was made by chance, during observations of globular clusters of the Milky Way with the HIRES (High Resolution Echelle Spectrometer) spectrometer installed on one of the Keck telescopes in October 2019, and archival images obtained by the CFHT telescope (Canada-France-Hawaii.

Analysis of the data showed that RBC EXT8 is one of the brightest globular clusters in M31, belongs to the galactic halo and is located at a distance of 27 kp from its center.. It is quite massive and compact, its age is more than eight billion years.. It turned out that the level of iron content in the cluster is about 800 times lower than that of the Sun, and about three times lower than that of the already known low-metal globular clusters. In addition, the accumulation contains extremely little magnesium, which is one of the elements produced during? -process, however, it shows an increased content of silicon, calcium and titanium compared to the Sun. All of these cluster properties are in poor agreement with current concepts of the minimum metallicity for globular clusters and the theory that massive globular clusters cannot form at such low metallicities..

Earlier, we talked about how metal-poor stars pointed to the alien origin of the globular cluster Omega Centauri and where the most metal-poor dwarf galaxy is located.

Alexander Voytyuk https: // nplus1. ru / Keywords:.