A recent study has shed light on the evolution of the Milky Way galaxy, revealing a significant milestone from its early history. Researchers examining star clusters near the galaxy’s core have uncovered evidence of a galactic merger that occurred approximately 11.8 billion years ago, when the universe was still in its infancy.
The merger involved a smaller dwarf galaxy, distinct from larger galaxies like the Milky Way, estimated to contain stars with a mass equivalent to 500 million times that of the sun at the time of the event. This merger marked the earliest-known galactic interaction for the Milky Way, demonstrating how the galaxy expanded not only through its own star formation but also by assimilating smaller galaxies within its gravitational influence.
Utilizing data from the Hubble and Gaia telescopes, scientists studied stellar clusters within the innermost 20,000 light-years of the Milky Way, analyzing their age, chemical composition, and trajectory. These stars, now part of the Milky Way, originated from a galactic merger that occurred about two billion years after the Big Bang.
Lead author Davide Massari highlighted the significance of this discovery, emphasizing the infusion of stars, interstellar gas, and dark matter into the Milky Way through the merger process. While the merger was peaceful in terms of stellar interactions, it triggered a burst of star formation through the collision of gases from the dwarf galaxy and the Milky Way.
The Milky Way has been involved in two other major galactic mergers, including the absorption of the Gaia-Sausage-Enceladus dwarf galaxy and ongoing interactions with the Sagittarius dwarf galaxy. These mergers have influenced the formation of our solar system and the Earth, underscoring the importance of understanding the Milky Way’s history in addressing fundamental questions about our origins.
