Computer graphic display of the intensity of light emitted by spiral galaxy M51, the Whirlpool Galaxy, & its companion NGC 5195. Intensity is represented by height. M51 is the peak" at right, with NGC 5195 at left; the small spikes surrounding the galaxies are foreground stars. In fact, M51's centre is so bright that its peak has been artificially truncated; the image highlights the complex structure in the galaxies' "foothills" summing 16 million picture elements (pixels) from several optical photographs obtained by the 1. 2 meter Schmidt telescope at Mt Palomar Observatory."