Giant, mysterious rippling wave detected in Milky Way by Gaia Telescope

How do stars trace the ripple?
Scientists followed the movement with young giant stars and Cepheid stars, whose brightness changes in a predictable manner over time. These stars move with the wave, suggesting that gas in the disc might also participate in the ripple. The stars may carry a “memory” of the wave from the gas they formed from.

Researchers liken the wave to a stadium crowd performing a wave. Red areas on Gaia’s maps correspond to stars at the wave’s peak, while blue areas show stars below the warped disc. White arrows indicate vertical star movements, representing how the wave passes through the galactic disc.

In the red areas, the stars are positioned more ‘upward’, and in blue areas the stars are more ‘downward’ in relation to the disc of the galaxy. The motions of the stars in the wave are made visible with the white arrows. What can be noticed, is that the peak of the upward motions (represented by the arrows) is slightly shifted relative to the physical distortion (indicated by the red/blue colours). (Image: ESA)

What might have caused the galactic wave?
The reason behind the ripple is unclear.  A past collision with a dwarf galaxy is a possible explanation, though further study is needed. The wave might also relate to the smaller Radcliffe Wave, a 9,000-light-year ripple closer to the Sun, though the connection is unclear.

Johannes Sahlmann, ESA’s Gaia Project Scientist, said the upcoming fourth Gaia data release will provide improved positions and motions for stars, including Cepheids. This will allow scientists to create even more detailed maps and deepen understanding of the Milky Way’s dynamic structure.

The find reveals our galaxy is teeming with movement, opening up patterns that stretch long beyond the Sun. Gaia's unprecedented 3D vision keeps revealing secrets of the Milky Way's past and present.