A recent study has shed light on the complex evolutionary history of the Milky Way galaxy. Scientists have uncovered evidence of a significant event that occurred approximately 11.8 billion years ago when a smaller galaxy was absorbed by the Milky Way. This event, marking the earliest known galactic merger of the Milky Way, highlights how the galaxy grew not only through internal star formation but also through the assimilation of smaller galaxies within its gravitational influence.
The smaller galaxy involved in this merger was classified as a dwarf galaxy, containing stars with a total mass equivalent to 500 million times that of the sun at the time of the merger. Researchers utilized the Hubble and Gaia telescopes to analyze stellar clusters within the innermost 20,000 light-years of the Milky Way, studying their age, chemical composition, and trajectory.
The merger, which occurred about two billion years after the Big Bang, added stars and interstellar gas to the Milky Way, fueling star formation and contributing to the presence of dark matter. According to lead author Davide Massari, the merger was relatively peaceful in terms of star collisions but triggered a burst of star formation due to the collision of gas from both galaxies.
It is believed that many stars originating from the dwarf galaxy still reside within the Milky Way, particularly in stellar clusters in the inner regions. The Milky Way has experienced two other significant mergers in its history, including the absorption of the Gaia-Sausage-Enceladus dwarf galaxy and ongoing interactions with the Sagittarius dwarf galaxy.
These galactic mergers have played a crucial role in shaping the Milky Way’s history and have impacted the formation of our solar system, emphasizing the importance of understanding the galaxy’s past in unraveling the mysteries of our cosmic origins.
