One of the biggest surprises to emerge from the application of
amplification process was the detection of faint shells around
otherwise apparently normal (but often isolated) elliptical galaxies.
These faint traces are thought to be evidence of ancient mergers.>
The shell-like structures around this otherwise undistinguished pair NGC 1549 and 1553 were also unexpected, and suggest that interaction rather than merger could also generate structures of this kind. These galaxies were listed in the Malin-Carter catalogue of ellipticals with shells.