A recent study has shed light on a significant event in the early history of the Milky Way galaxy. Scientists have discovered that approximately 11.8 billion years ago, during a time when the universe was much younger, the Milky Way absorbed a smaller galaxy. This merger, the earliest known for the Milky Way, contributed to the galaxy’s growth by incorporating stars from the smaller galaxy into its own.
The smaller galaxy involved in the merger was classified as a dwarf galaxy, containing stars with a mass equivalent to 500 million times that of the sun at the time of the merger. This dwarf galaxy, named Low-energy-Kraken-Heracles (LKH), merged with the Milky Way about two billion years after the Big Bang.
Using data from the Hubble and Gaia telescopes, researchers studied stellar clusters near the Milky Way’s center to analyze their age, chemical composition, and trajectory. The findings confirm that the merger event played a crucial role in the early development of the Milky Way by introducing a significant number of stars and interstellar gas, including dark matter.
Lead author Davide Massari noted that while the merger was peaceful in terms of star collisions, it triggered the formation of many stars through the interaction of gases from both galaxies. He also highlighted the presence of stars from the dwarf galaxy still hidden within the Milky Way, particularly in stellar clusters in the inner regions.
The Milky Way has been involved in other major mergers in its history, including the absorption of the Gaia-Sausage-Enceladus dwarf galaxy and ongoing interactions with the Sagittarius dwarf galaxy. Massari emphasized the impact of these mergers on the formation of our solar system and the broader question of humanity’s origins.
Understanding the Milky Way’s past is crucial in unraveling the mysteries of our cosmic origins and the formation of celestial bodies, including Earth. This study provides valuable insights into the complex evolution of our galaxy and its continuous interaction with neighboring galaxies over billions of years.