The international team of astrophysicists found that the metallicity is the content of elements heavier than helium and hydrogen – the interstellar medium of our galaxy is heterogeneous. The article of scientists about this unusual property of the Milky Way was published in the journal Nature.
The nucleosynthesis process in the stars enriches the interstellar medium – initially usually consisting only of hydrogen and helium – atoms of heavier elements. According to the existing models, the interstellar medium of the Milky Way is characterized by a uniform distribution of the gas received from the outside of the galaxies, gas enriched with nucleosynthesis, and dust, obtained from the condensation of the atoms of heavy elements.
Researchers from the University of Geneva together with colleagues from the USA, France and Chile appreciated this ratio in reality for the atmosphere of 25 stars based on two telescope data – Hubble and VLT (Very Large Telescope). In order to measure the content of dust, scientists applied a new method. “In order to take into account the overall ratio of gas and dust, some elements are such as iron, zinc, titanium, silicon and oxygen – were observed simultaneously. After that, we could estimate the share of metals in dust and add it to the available estimates to establish a common relationship” , – told the lead author of the study of Annaliza de Sia.
It turned out that the interstellar medium is not homogeneous. Moreover, in some regions, the metallicity was only 10 percent of solar. The discovery, emphasize the scientists, will force the models of the evolution of galaxies – and the Milky Way in particular – in which it was previously believed that gas in the interstellar medium “stirred” evenly.