(ORDO NEWS) — Studying the large-scale structure of our galaxy is not easy. We do not have a clear idea of the shape and features of the Milky Way because we live inside it. But we have some advantages.
From within, we can conduct detailed studies of the Milky Way’s stellar population and its chemical composition.
This gives us the tools we need to compare our galaxy with the many millions of other galaxies in the universe.
To narrow down the sample size, the scientists left only galaxies with a total mass similar to that of the Milky Way.
They then ruled out galaxies with very different “bulge to total volume ratios”. And finally, the researchers chose galaxies of the same type according to Hubble’s classification.
As a result, the team was left with 138 galaxies that look similar to ours.
The scientists loaded the data into a model that predicts star formation by taking into account how stellar winds carry away excess gas from star systems that can be pulled toward the center of galaxies.
The model also took into account the chemical composition and metallicity of materials in various regions of galaxies.
The study found that 56 out of 138 galaxies are very similar to ours. These galaxies are characterized by the fact that in the outer regions, star formation occurs over a long time interval.
The inner region experienced a period of intense star formation early in the galaxy’s history. It was caused by a flow of gas drawn inward toward the center from the outer region.
Later there was a much slower period of star formation in the core, based on the recirculation of gas blown out by older stars in the outer region.
The new stars, which are made of recycled material, have a higher level of metallicity and contain heavier elements that are lacking in the first generation of stars.
The rest of the galaxies, upon closer inspection, turned out to be not like the Milky Way. They were divided into two categories.
The first category, which included 55 out of 138 galaxies, are galaxies that do not have differences between their inner and outer regions.
In these galaxies, star formation occurs evenly, the stars in the inner and outer regions seem identical.
27 out of 138 galaxies fell into the second category. They lack any significant period of recent star formation from recycled material in their cores.
This means that there is no radial influx of gas from the outer regions in these galaxies. They have completed most of their star formation in the past, which hints that they may be older than the Milky Way.
Scientists also offer another possible explanation – the presence of an active galactic nucleus, which can suppress star formation in the inner regions of galaxies.
This study opens up many new possibilities for studying galactic evolution. It shows that we are not entirely unique. Studying these doppelgangers can help us learn more about our own home.
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