Whirlpool Galaxy

The Whirlpool Galaxy, M 51, is one of the prettiest galaxies in the northern sky in the unremarkable constellation Canes Venatici (hunting dogs). It is about 31 million lightyears away and has a diameter of about 76 000 lightyears. Actually, it is not one galaxy but two galaxies whose gravitational interaction is responsible for the unusual shape. The main galaxy is a grand design spiral galaxy with two prominent arms, which exhibits unusually active star formation. This is evident from the large number of young and massive stars giving rise to the blue regions in the spiral arms. In addition there are dust lanes tracing the spiral arms and pink specks that represent emission nebulae.

The smaller companion galaxy is an irregular galaxy, NGC 5195, which seems to be attached to the end of one of the spiral arms of the main galaxy. Actually, this companion is sitting slightly behind the disk of the main galaxy, and there is evidence that is has crossed the disk som 50 or 100 million years ago. The gravitational interaction of the two galaxies affects the structure of the two galaxies and is responsible for the weak nebulosity in the lower part of the image – these are so-called tidal tails consisting of streams of stars that have been thrown out of the regular orbits and are moving away from the galaxies.

This is an RGB image with a total of 13 hours of exposure time, taken with our Planewave CDK17 at the TURMX observatory. The three color channels have about the same total exposure time and we did not use separate luminance exposure in this case. The processing focused on showing the weak light emitted from the star streams in the lower part of the image surrounding the companion galaxy. Definitely check out the full-screen view by clicking on the image.