A recent study sheds light on the complex evolution of the Milky Way galaxy, which is home to billions of stars, including the sun. Scientists have uncovered evidence of a significant event in the Milky Way’s past, revealing that approximately 11.8 billion years ago, a smaller galaxy was engulfed by our galaxy during its early stages of development.
This ancient galactic merger, the earliest known in the Milky Way’s history, highlights how the galaxy expanded not only through internal star formation but also by assimilating smaller galaxies through gravitational forces. 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, making it a quarter of the Milky Way’s size at that period.
Utilizing data from the Hubble and Gaia telescopes, researchers examined stellar clusters within the Milky Way’s innermost 20,000 light-years, studying their age, chemical composition, and trajectory. These stars were incorporated into the Milky Way after the galactic merger, which occurred about two billion years post-Big Bang, originating from a dwarf galaxy named Low-energy-Kraken-Heracles (LKH).
Lead researcher Davide Massari highlighted the significance of this discovery as the first merger event in the Milky Way’s early history. The study suggests that the merger provided a substantial influx of stars, interstellar gas, and dark matter, fueling star formation in the galaxy.
Massari explained that while the merger was peaceful in terms of stars, with no collisions, the interaction of gas from both galaxies likely triggered massive star formation. The Milky Way has been involved in two other major galactic mergers, further shaping its evolution over billions of years.
Understanding the Milky Way’s history, including its mergers with other galaxies, contributes to answering fundamental questions about the origins of our solar system and Earth. This ongoing research offers valuable insights into the galaxy’s past and its role in the formation of celestial bodies.