The Hubble Space Telescope has stepped on the tails of 12 interacting galaxies and found them to be studded with the shining diamonds of young star clusters —scientists compare the phenomena to cosmic "strings of pearls."
When spiral galaxies interact, either through direct collision or close encounter, their spiral arms unravel. The gravitational force that a galaxy wields is vast, so when two galaxies become close, the gravitational tides that are raised tug on those spiral arms, pulling them out to form long "tails" that can stretch for many tens of thousands of light-years.
