Galactic Archaeology: Pinpointing the Milky Way's Last Major Collision
A new study refines the timeline of our galaxy's violent past, revealing how collisions can shred stellar discs.
Researchers from the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and the Institute of Space Studies of Catalonia (IEEC) have published groundbreaking findings in the Monthly Notices of the Royal Astronomical Society. Using advanced simulations, the team has demonstrated that galaxy collisions are capable of completely or partially destroying stellar discs.
The findings, combined with observational data on star clusters, improve predictions for the timing of the last significant galactic collision involving the Milky Way.
The Dynamic Disc
The Milky Way's disc is a rotating, pancake-shaped system of stars that rotates at over 220 km/s. A key question for astronomers has been: when did this rotating disc actually form?
A major breakthrough came in 2018 with data from the Gaia mission, which confirmed that a violent collision with a smaller galaxy—known as the Gaia-Sausage-Enceladus (GSE) merger—occurred about ten billion years ago. This event played a crucial role in shaping the structure of the Milky Way we see today.
"The new simulations show that these galactic mergers are far more disruptive than previously thought, capable of tearing apart the very structure of a galaxy's disc."
What This Means
By refining our understanding of how stellar discs are destroyed during collisions, researchers can now more accurately date the last major merger in the Milky Way's history. This provides a clearer picture of the galaxy's evolution and the violent events that shaped our cosmic home.