A recent study has shed light on the complex history of the Milky Way galaxy, home to billions of stars, including our own sun. Researchers have uncovered evidence indicating that the Milky Way absorbed a smaller galaxy approximately 11.8 billion years ago, when the universe was relatively young. This marks the earliest galactic merger known to have occurred in the Milky Way’s past.
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. Through the use of Hubble and Gaia telescopes, scientists examined stellar clusters within the Milky Way, analyzing their age, composition, and trajectory across a region spanning 20,000 light-years from the galaxy’s core.
The merger, which occurred about two billion years after the Big Bang, introduced new stars and interstellar gas to the Milky Way, fueling star formation and contributing to the presence of dark matter. This discovery contradicts previous debates regarding whether the Milky Way’s growth was driven by internal star formation or external mergers.
According to lead researcher Davide Massari, the merger was a relatively peaceful event for stars, but the collision of gases likely triggered significant star formation. It is believed that stars originating from the dwarf galaxy are still present within the Milky Way, particularly in stellar clusters in its inner regions.
In addition to this ancient merger, the Milky Way has been involved in two other significant galactic mergers. Understanding these cosmic events not only sheds light on the galaxy’s past but also provides insights into the formation of our solar system and Earth. By piecing together the Milky Way’s history, researchers aim to answer fundamental questions about the origins of our universe.