A recent study reveals that the Milky Way, a vast spiral galaxy hosting a multitude of stars, including our sun, underwent a significant galactic merger around 11.8 billion years ago. Scientists examining star clusters near the Milky Way’s center have uncovered evidence of this ancient event, shedding light on the galaxy’s growth through mergers with smaller galaxies, in addition to its own star formation.
The smaller galaxy involved in the merger, classified as a dwarf galaxy, contained stars with a mass equivalent to 500 million times that of the sun at that time, representing a fraction of the Milky Way’s size back then. Researchers utilized the Hubble and Gaia telescopes to analyze stellar clusters within the Milky Way’s innermost 20,000 light-years, studying their age, chemical composition, and trajectory.
Referred to as Low-energy-Kraken-Heracles (LKH), the dwarf galaxy merged with the Milky Way approximately two billion years after the Big Bang. This discovery marks the earliest-known galactic merger experienced by our galaxy, according to astrophysicist Davide Massari, the lead author of the study published in Nature Astronomy.
The study suggests that the merger played a crucial role in infusing the Milky Way with stars, interstellar gas, and dark matter, fueling star formation. While the merger was peaceful in terms of stars, it triggered the formation of many stars due to the collision of gas from LKH and the Milky Way.
Furthermore, the Milky Way has been involved in two other significant galactic mergers, including one with Gaia-Sausage-Enceladus and ongoing interactions with the Sagittarius dwarf galaxy. These mergers have influenced the formation of our solar system and Earth, highlighting the importance of understanding the Milky Way’s history in unraveling the mysteries of our origins.