ESA detects giant wave in the Milky Way, possibly from a collision with a smaller galaxy
Over the years, scientists have established that the stars in our galaxy rotate around its center within a warped galactic disk. In 2020, Gaia revealed that this warped disk wobbles over time.
Now, Gaia has revealed that there is a great wave moving through the galaxy. Gaia’s data show that this wave is rippling outward from the galaxy’s center and affecting stars as far as 30,000 to 65,000 light-years away from the center.
The telescope’s 3D edge-on map of the Milky Way revealed an up-and-down rippling. This provides proof of the great wave. Using Gaia’s data, astronomer Eloisa Poggio and her team tracked the motion of the wave.
They did this by studying the position and motion of young giant stars and Cepheids. Cepheids are stars whose brightness changes predictably and can be seen from far away. The young stars and Cepheids appeared to be moving with the wave.
Given that these stars are formed from interstellar gas, scientists think that the gas that formed these stars was also moving in the same wave-like pattern. The cause of the wave, however, is yet to be discovered. A possible explanation is that the wave was formed as a result of a past collision with a dwarf galaxy.
Another explanation is that the wave is related to the Radcliffe Wave. The Radcliffe Wave is a smaller-scale ripple seen 500 light-years away from the Sun. Scientists will dig deeper. A new Gaia release expected in December 2026 will advance our understanding of the position and motion of stars in the Milky Way.
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Image credit: ESA/Gaia/DPAC, S. Payne-Wardenaar, E. Poggio et al (2025).
