Our Milky Way galaxy never sits still: it rotates and wobbles. And now, data from the European Space Agency's Gaia space telescope reveal that our galaxy also has a giant wave rippling outwards from its center.

We've known for about a hundred years that the galaxy's stars rotate around its center, and Gaia has measured their speeds and motions. Since the 1950s, we've known that the Milky Way's disk is warped. Then, in 2020, Gaia discovered that this disk wobbles over time, similarly to the motion of a spinning top.

And now it has become clear that a great wave stirs the motion of stars in our galaxy over distances of tens of thousands of light-years from the sun. Like a rock thrown into a pond, making waves ripple outwards, this galactic wave of stars spans a large portion of the Milky Way's outer disk.