When galaxies collide, they pass through one another like ghosts moving through a wall.
Their stars are spaced so far apart that they rarely touch. However, the pull of gravity distorts the galaxies, spraying their stars across space.
Canadian Heritage Information Network
Australian Museums & Galleries Online, Australia; Centre of the Universe; Gemini Observatory, Hawaii; Glenbow Museum; The Manitoba Museum; National Research Council Canada; Planétarium de Montréal