Our Milky Way is constantly in motion: it spins, it tilts, and, as new observations reveal, it ripples. Data collected by the European Space Agency’s Gaia space telescope show that our galaxy is not only rotating and wobbling but also sending out a vast wave that travels outward from its center.
For about a century, astronomers have known that the Milky Way’s stars orbit its core, and Gaia has precisely tracked their speeds and trajectories. Since the 1950s, scientists have also recognized that the galactic disc is not flat but warped. Then in 2020, Gaia uncovered that this warped disc slowly oscillates over time, similar to the motion of a spinning top.