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Loading contentThe gravitational give-and-take of galaxies passing close without fully merging — drawing out tidal tails and bridges, triggering star formation, and, in a direct hit, punching out a ring galaxy.
Facts on this topic will be cited from these primary and reference sources.
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.