A recent study has revealed a significant milestone in the history of the Milky Way galaxy. Researchers have found evidence that approximately 11.8 billion years ago, when the universe was relatively young, the Milky Way absorbed a smaller dwarf galaxy. This event marked the earliest-known galactic merger for our galaxy, showcasing its growth not only through internal star formation but also by assimilating smaller galaxies within its gravitational field.
The dwarf galaxy involved in the merger, named Low-energy-Kraken-Heracles (LKH), was estimated to contain stars with a mass equivalent to 500 million times that of the sun at the time of the merger. This was roughly a quarter of the size of the Milky Way during that period. Using data from the Hubble and Gaia telescopes, researchers studied stellar clusters within the Milky Way’s innermost 20,000 light-years, analyzing their age, chemical composition, and trajectory.
The study highlighted the impact of the merger on the Milky Way’s early development, indicating that it introduced a substantial number of stars and interstellar gas, essential for fueling star formation and contributing to the presence of dark matter. While the merger was relatively peaceful for stars, it triggered significant star formation due to the collision of gases from both galaxies.
The Milky Way has been involved in multiple galactic mergers, including one with the Gaia-Sausage-Enceladus dwarf galaxy and ongoing interactions with the Sagittarius dwarf galaxy. Each merger has played a role in shaping the Milky Way’s evolution and has influenced the formation of our solar system, emphasizing the importance of understanding the galaxy’s history in answering fundamental questions about our origins.