The motions of stars in the Milky Way have revealed a giant outward ripple, set off by a massive event sometime in our galaxy's wild past.

In a new analysis of data collected by the Gaia space-mapping spacecraft and a database of pulsating stars, astronomers have measured the up-and-down motions of stars in the outer regions of the galactic disk and found patterns consistent with a wave-like corrugation.

What generated this ripple is unknown, but one possible culprit is an encounter with another galaxy – likely the Sagittarius dwarf galaxy currently interacting with the Milky Way – punching through the galactic disk, like a pebble dropping into a pond.

Related: 'Family Tree' of The Milky Way Reveals The Fate of The Mysterious Kraken Galaxy

This finding suggests, once again, that

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