An international research team analyzed 39 globular clusters in our galaxy and found evidence of a merger with another galaxy called 'Low-Energy Kraken-Hercules' (LKH) about 12.3 billion years ago. This is about 1.8 billion years earlier than the previously known oldest Milky Way merger event, Gaia-Sausage-Enceladus (GSE). The mass of the LKH galaxy was similar to that of GSE, and it is analyzed that globular clusters concentrated within about 20,000 light-years from the center of our galaxy constitute it. This study provides important clues for understanding the early growth process of our galaxy, and it is expected that more detailed history can be revealed through further analysis such as internal vibration analysis of stars.
