On Monday, Nature Astronomy published an article on the early evolutionary stages and mergers of our galaxy, the Milky Way. The research used Hubble observations and advanced statistical models to determine the stars’ ages and chemical compositions.
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Using data from the Hubble Space Telescope, a team of astronomers discovered evidence of a merger that took place about 11.8 billion years ago, just 2 billion years after the Big Bang.
To achieve these results, the scientists analyzed 39 dense groups of stars, known as globular clusters, which can act as cosmic archaeological sites, according to the article led by Davide Massari of the Bologna Observatory of Astrophysics and Space Science in Italy.
The Milky Way is now a huge spiral galaxy that is home to hundreds of billions of stars, but it was not always so large. It has grown by forming new stars from its gas clouds, as well as by incorporating stars, gas and dark matter from other galaxies through mergers.
The most recent massive merger in its history occurred with the Sagittarius dwarf galaxy. It began more than 6 billion years ago and continues today. In this study, the researchers went even further back in time and identified several events in the history of the galaxy.
One of them is associated with the progenitor of the Milky Way, while another occurred when it absorbed another dwarf galaxy called “Gaia-Sausage-Enceladus” 10 billion years ago. This ancient merger greatly affected the structure of the stellar disk of our galaxy.
Both observations and simulations had suggested another major merger, although the specific details have been the subject of intense debate. This is precisely what the study seeks to clarify, concluding that a dwarf galaxy merged with the young Milky Way during the early stages of its evolution.
In the article, the researchers reveal “a fundamental element” that contributed to the formation of the young Milky Way about 12 billion years ago, a merger that would provide a clearer timeline of the galaxy’s initial growth, the magazine said.
“Our home is the Milky Way, but we do not know how our house was built. In this article, we discovered where the first significant batch of bricks came from: a dwarf galaxy that we call ‘Low-Energy-Kraken-Heracles’ (LKH),” Massari said.
The Hubble data — along with other data from the ESA’s Gaia mission and mathematical models — made it possible to distinguish a population of globular clusters that differs from the rest.
“These are the clusters that were born in LKH and tell us when that galaxy was devoured by ours, as well as what its mass was,” said Chiara Zerbinati of the University of Bologna.
The system is estimated to have had a stellar mass similar to that of the “Gaia-Sausage-Enceladus” dwarf galaxy and deposited most of its material in the inner regions of the Milky Way. A merger of such magnitude at such an early stage in the Milky Way formation has profound implications for its evolution.
“Some previous studies have argued that the early stages of the evolution of our galaxy were marked solely by stars born in our galaxy. In this work, we have shown that stars born in external galaxies must also be taken into account,” said Carme Gallart of the University of La Laguna.
The authors of the research published in Nature Astronomy noted that there may have been smaller merger events before the “Gaia-Sausage-Enceladus” merger.
teleSUR/ JF
Source: EFE
Source: teleSUR
