Stargazing Evening: October 2025

Our Galaxy in motion: Ridges, ripples and spirals in the Milky Way

Our home galaxy, The Milky Way is not static; it is constantly in motion, and its life is shaped by complex interactions between internal dynamical processes and external forces. The European Space Agency’s Gaia mission has revolutionised our understanding of the Milky Way by mapping the positions and motions of ~1.8 billion stars, and one of the key findings is that our Galaxy shows signs of a recent disturbance. Similar to how a stone thrown into a pond will create ripples which spread across the surface, Gaia has revealed massive ripples in the position and motion of stars in the Galactic disc, expect that these span tens of thousands of light years, and will take billions of years to mix away. In this talk, I will show the data from Gaia and ground based telescopes which revealed these distortions, and then how we are trying to model these interactions with large numerical galaxy simulations.