The strong spiral character of the Whirlpool Galaxy, M51 (on the right), is thought to be due to its interaction with its companion galaxy, NGC 5195 (on the left). Both are about 23 million light-years away in the constellation Canes Venatici, just below the end of the Big Dipper's handle. Several other galaxies appear faintly in the background, well beyond these two.
120 minutes L and 146 minutes RGB starting on 2012-05-18 and 2012-05-19 using a QSI 583 from northern New Jersey through an Astro-Physics 155mm refractor at f7.1. North is to the left. ©2012