A recent study sheds light on the complex history of the Milky Way galaxy, home to billions of stars, including our sun. Researchers have uncovered evidence suggesting that the Milky Way engulfed a smaller galaxy approximately 11.8 billion years ago, when the universe was still young.
This early galactic merger, the first known for the Milky Way, highlights how the galaxy not only formed stars internally but also grew by assimilating smaller galaxies through its gravitational force. The smaller galaxy, classified as a dwarf galaxy, contained stars equivalent to 500 million solar masses at the time of the merger, a quarter of the Milky Way’s size then.
Using the Hubble and Gaia telescopes, scientists studied stellar clusters within the Milky Way’s innermost 20,000 light-years to analyze their age, composition, and trajectory. These stars originated from the merger about two billion years after the Big Bang event that initiated the universe.
Lead researcher Davide Massari stated that the merger injected a significant number of stars and interstellar gas into the Milky Way, fueling star formation and contributing to the galaxy’s growth. While the merger was peaceful in terms of star collisions, it triggered intense gas interactions that spurred star formation.
The Milky Way has been involved in two other major mergers, including one with 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 Earth, underscoring the importance of understanding the Milky Way’s history in unraveling our cosmic origins.