In work recently published in The Astrophysical Journal, astronomers at the Max Plank Institute for Astronomy (MPIA) in Heidelberg, Germany, have revealed two possible initial building blocks of our Milky Way that are still detectable.
These two components, named Shakti and Shiva (Hindu gods of creation of the world), are protogalactic fragments, i.e. massive clumps of gas and dust that merged with a young version of our galaxysometime between 12 and 13 billion years ago, when most galaxies were forming in the universe.
The structures were identified by combining data collected by the European Space Agency’s (ESA) Gaia astrometric satellite with data from the Sloan Digital Sky Survey (SDSS) database. To Team Leader Khyati Malhan, “What was really surprising was that we were able to detect these ancient structures.”stated in the statement
Archeology of the Milky Way through star tagging
The surprise of the astronomers is justified. After all, the Milky Way has undergone significant changes over these billions of years, and the ability to group these ancient stars together is an extraordinary feat. This fact occurred in the year 2022 when Gaia was doing some kind of galactic archaeology. A new study has labeled stars based on when they merged with our galaxyeven before it assumed its spiral shape.
Near the heart of the Milky Way, Shakti and Shiva have similar orbital trajectories and each has about 10 million suns between 12 billion and 13 billion years old. Because they were born when the universe was composed mostly of hydrogen and helium, these stars lack metalswhich is formed by the fusion of these two primordial gases.
Naturally, the first generation of stars had already died, exploding into supernovae and spreading the heavy elements they had formed over the ages through the universe. And these metals organized themselves into a second generation of stars that followed the first, a process of continuous life, death, and rebirth. Astronomers can thus estimate the age of stars simply by observing the amount of their metals.
Differences between Shakti and Shiva
Shakti stars are further from the center of the Milky Way and are more circular than Shiva.Fonte: NASA/JPL-Caltech; ESA/ATG media lab
Although it was already known that more than 12 billion years ago the Milky Way may have been composed of long filaments of dispersed gas and dust, Gaia showed that “the stars at the heart of our galaxy are metal-poor, That’s why we call this region the ‘poor old heart’ of the Milky Way”said research co-author Hans-Walter Rix, one of 2022’s galactic archaeologists.
The individualization of Shakti and Shiva made it possible to identify not only the initial stages of the growth of our galaxy, but also to understand that there are some fundamental differences between its oldest fragments.
Did you like the content? So stay up to date with the latest studies about our galaxy, like this one here on TecMundo, and take the opportunity to see a simulation of the collision between the Milky Way and Andromeda.
