A recent study has shed light on the complex evolution of the Milky Way galaxy, home to billions of stars, including our sun. Researchers have identified a significant event in the galaxy’s history, revealing that approximately 11.8 billion years ago, the Milky Way absorbed a smaller galaxy during its early formation stages when the universe was much younger.
This merger, the earliest known in the Milky Way’s history, involved a dwarf galaxy with a mass equivalent to about 500 million times that of the sun at the time of the event. The researchers utilized data from the Hubble and Gaia telescopes to study clusters of stars near the Milky Way’s center, analyzing their age, composition, and trajectory across a region spanning 20,000 light-years.
The merged stars from the dwarf galaxy, named Low-energy-Kraken-Heracles (LKH), contributed to the growth of the Milky Way about two billion years after the Big Bang. Lead researcher Davide Massari highlighted the discovery as the first galactic merger experienced by the Milky Way in its early stages.
The study suggests that the merger infused the Milky Way with a significant number of stars, interstellar gas, and dark matter, fueling star formation. While the merger was relatively peaceful for stars, it triggered an ‘explosive’ collision between gases from the two galaxies, leading to the formation of new stars.
Massari noted that remnants of stars from the dwarf galaxy likely exist within the Milky Way, particularly in stellar clusters within the galaxy’s inner regions. The Milky Way has also 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 played a crucial role in shaping the Milky Way’s evolution and could offer insights into the origins of our solar system and Earth. Understanding the galaxy’s past is essential in answering fundamental questions about our cosmic origins.