What happens when galaxies collide?
A galaxy collision involves gravitational distortion, gas compression and possible merger of the galaxies.
Formation, motion and physical explanation
Direct star-star collisions are unlikely because stars are sparse, but their orbits still change. Gas clouds collide and may increase star formation.
Evidence, applications and limits
Tidal tails move material and dynamical friction brings nuclei closer. The process lasts hundreds of millions of years and depends on encounter geometry. Conclusions about distant objects rely on testing images, spectra, time variation and physical models together.
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