Astronomers have discovered the poor old heart of the Milky Way

A team of astronomers from the Max Planck Institute for Astronomy has succeeded in identifying the "poor old heart of the Milky Way", a population of stars that has survived in the core of the Galaxy since its formation.

Our home Galaxy, the Milky Way, has been forming for the past 13 billion years - almost as long as the Universe has existed. In recent decades, astronomers have been able to reconstruct many stages of galactic history, and their methodology is not too different from the dating methods used by archaeologists.

So, for example, having excavated an ancient city, scientists can determine which buildings were built earlier and which later. This is indicated by the location of the buildings (logically, the oldest part of Moscow is located around the Kremlin) and the materials or construction methods used to create them. "Space archaeologists" in this regard act in the same way, determining the age of stars by their chemical composition and location in the universe.

To reconstruct the history of the Milky Way from the beginning, researchers from the Institute for Astronomy of the Max Planck Society (Germany) determined the age of thousands of the oldest observable stars in the subgiant stage. This allowed them to "look back in time" 11 billion years, to the time of the Milky Way's merger with a dwarf galaxy whose remnants were discovered in 2018.

Since the oldest stars contained quite a lot of heavy elements, astronomers suggested that they were not the first in history at all and there were already several generations of early stars before them, saturating interstellar space with metal atoms after the explosion. This is consistent with the assumption that before the formation of the Milky Way there were three or four protogalaxies, formed not far from each other and eventually merged together. It was they who became the "heart" of the Milky Way, preserved in the center of our Galaxy, and eventually scientists were able to find it.

It turned out, as suggested by the researchers, the "poor old heart of the Milky Way" is located at a distance of about 30 thousand light years from the center of the Galaxy and represents a group of metal-poor stars whose age exceeds 12.5 billion years.

Perhaps, having obtained additional data, scientists may even be able to determine to which of the protogalaxies belong to each star, which will make it possible to clarify the origin of the entire Milky Way.