A group of astronomers from the University of Geneva (UNIGE) have discovered an unusual property of the Milky Way: the interstellar medium of our galaxy is heterogeneous.
Earlier, in theoretical models, there was information that in the interstellar medium, elements heavier than helium and hydrogen are homogeneously mixed and have reached the level of chemical enrichment. A similar thing happens in the sun’s atmosphere: it is called solar metallicity.
But the authors of the new work denied this information: they found out that the gases do not mix so much. This will affect the previously constructed models of the evolution of galaxies.
The process of nucleosynthesis – the formation of nuclei of chemical elements heavier than hydrogen – enriches the interstellar medium, usually consisting only of hydrogen and helium, also with atoms of other heavy elements.
The authors of the new work estimated how correct this theory is: they used the atmosphere of 25 stars and studied it with two telescopes – Hubble and VLT (Very Large Telescope). In order to measure the dust content, scientists have applied a new method.
In order to account for the overall gas to dust ratio, several elements – such as iron, zinc, titanium, silicon and oxygen – were observed simultaneously. After that, we could estimate the proportion of metals in dust and add it to the available estimates to establish the overall ratio.
Annalize de Sia, lead author of the study
As a result, it turned out that the interstellar medium is not homogeneous. Even more – in some regions the metallicity was only 10% of the solar one.