By making a detailed analysis of the composition and motion of 556 stars from its composition, American astronomers have found convincing evidence of an ancient collision of the Andromeda Nebula (M 31) with a large neighboring galaxy. They presented their findings at the 240th meeting American Astronomical Society in Pasadena.
Galaxies grow by collecting material from nearby objects (other galaxies and dense star clusters called globular clusters) and occasionally experience disastrous mergers with larger neighbors. These events leave traces in the form of unusual stellar associations that astronomers call tidal remnants. These could be long streams or curved features near the emerging galaxy. In this case, these are the northeast, west, southeast shelves of the galaxy, as well as the Giant Andromeda star stream.
Ivanna Escala of Carnegie Observatory and colleagues studied these features that helped them reconstruct the history of the galaxy and its former neighbor that shaped the appearance and composition of current Andromeda. “The remnants of such mergers can be identified by studying the motion and chemical composition of stars. In general, all this information serves as a kind of fingerprint identifying stars that joined the galaxy as a result of the collision,” Escala explained. Press release Carnegie Institution. “For the first time, we have studied in detail the chemical composition and motion of stars in these regions of our nearest galactic neighbor, and have convincingly shown that the northeast shelf is a tidal remnant composed primarily of collision fragments. Our results show that the Giant Stellar Stream and northeast shelf are the first and second layers of accumulating material. It is consistent with simulations showing that
The new analysis confirms previous assumptions about Andromeda’s turbulent past and helps astronomers understand how material from collisions determines the galaxy’s appearance and evolutionary history.