The researchers discovered an unknown merger between the Milky Way galaxy and the galaxy Kraken 11 billion years ago.
The Milky Way contains more than 100 billion stars. At least dozens of times over the past 12 billion years, the Milky Way has collided with neighboring galaxies and merged, “devouring” neighboring stars and mingling them in star nurseries. After each merger, the Milky Way’s shape, size, and motion changed forever, becoming the characteristic spiral shape it is today.
In a study published in the Monthly Notices of the Royal Astronomical Society, scientists investigate the cause of that spiral. Using artificial intelligence (AI) to match clusters by age, motion, and chemical composition, the team found evidence of five large-scale galaxy mergers (each comprising 100 million). star), dating back more than 10 billion years, includes an ancient collision never described before.
The largest collision in the history of the Milky Way
The newly discovered collision with the galaxy Kraken not only helped fill the mysterious genealogical tree of the Milky Way galaxy, but also helped astronomers string the shapes of our galaxy in the early days. According to lead researcher Diederik Kruijssen, an astronomer at Heidelberg University in Germany, the Kraken collision event is the most important merger the Milky Way has ever experienced. The merger took place 11 billion years ago when the Milky Way was four times smaller than it is today.
In the new study, Kruijssen and colleagues used computer simulation to analyze all globular clusters, long-standing solid spheres containing up to 1 million stars that form at the same time within the Milky Way. Our galaxy consists of at least 150 of these clusters. Astronomers claim that they are “fossils” of ancient galaxies “swallowed up” by the Milky Way in history.
The team developed an AI algorithm to identify a globular cluster based on the common characteristics of the star. First, they ran the algorithm on thousands of simulated galaxies. After the algorithm can accurately predict the formation, evolution, and destruction of globular clusters in simulated galaxies, they use it for the Milky Way.
Using Gaia space probe data, an algorithm that analyzes the age, motion, and chemical composition of known globular clusters to reconstruct the mergers that brought them there. The team’s analysis accurately predicts 4 past mergers of the Milky Way, including the Gaia merger that contributed to the addition of billions of stars to our galaxy 9 billion years ago, along with the Kraken merger.
According to the results of the researchers, Kraken is the oldest and largest galactic collision in the history of the Milky Way. This merger happened when the Milky Way was only a fraction of its current size, resulting in 13 globular clusters still identifiable today. The team suspects there have been at least 15 other mergers in the past, each comprising at least 10 million stars.