A recent study has shed light on the early evolution of the Milky Way galaxy. Researchers have found evidence of a significant event that took place around 11.8 billion years ago when the universe was much younger. This event marks the earliest known galactic merger for the Milky Way, where a smaller dwarf galaxy was absorbed, contributing to the growth of our galaxy.
By examining star clusters near the center of the Milky Way, scientists determined that the dwarf galaxy contained stars with a mass equivalent to 500 million times that of the sun at the time of the merger. This smaller galaxy was about a quarter of the size of the Milky Way back then.
Using data from the Hubble and Gaia telescopes, researchers studied stellar clusters within the innermost 20,000 light-years of the Milky Way. These stars were part of the galactic merger that occurred approximately two billion years after the Big Bang. The dwarf galaxy that these stars originated from was named Low-energy-Kraken-Heracles (LKH).
Lead author Davide Massari noted that this research reveals the Milky Way’s first merger event during its early stages. The study suggests that the merger injected a large number of stars, interstellar gas, and dark matter into the Milky Way, fostering star formation.
Massari explained that while the merger was peaceful for stars, the collision of gases likely triggered the formation of many new stars. The Milky Way has been involved in two other major galactic mergers, including the absorption of the Gaia-Sausage-Enceladus dwarf galaxy and the ongoing merger with the Sagittarius dwarf galaxy.
According to Massari, reconstructing the Milky Way’s past helps answer fundamental questions about our origins and the formation of celestial bodies like Earth.