The Whirlpool Galaxy is an interacting grand-design spiral galaxy. A grand design spiral galaxy is a type of spiral galaxy with prominent and well-defined spiral arms, as opposed to multi-arm and flocculent spirals which have subtler structural features. Why this galaxy is a grand-design spiral is pretty clear but it is also an interacting galaxy. Interacting galaxies are those whose gravitational fields result in a disturbance of one another.
M51(a and b) are stimated to lie at a distance of 23 ± 4 million light-years from us, well, that's far far away and actually a long time ago, but they're not the only galaxies in this picture. If you look carefully to the image it is possible to depict at least four more galaxies:
- NGC 5229 (on the margin top right partially off frame) located at 17 million ly.
- NGC 5169 second on the left of M51 located at 112 million ly.
- NGC 5173 third on the left from M51, don't mistake it for a star. 111 million ly.
- NGC 5198 left and slightly up from M51, 116 million ly.
- IC 4264 located first on the left from M51 at a distance of 125 million ly.
Now that's far far far far far away. By the time the light left this galaxies, we were in the Aptian age. The continents were still splitting appart in the lower Cretaceous and the dinosaurs were ruling the Earth. Of course no sight of nothing similar to a human/monkey being until a "few" years later and yet here we are, catching the light from that time.
The shot was not really good, too noisy due to light pollution, and the night was not clear though. That's the reason why I didn't try to process it until now. However, recent discoveries in my processing pipeline gave me some ideas to give it a go. It is composed by 30 lights of 120" each, 40 darks and 40 bias with the 70mm refractor (ETX-70) mounted on the HEQ-5 and taken with a Nikon D3100 unmodded. The processing was performed with StarTools and Photoshop.
As usual, ENJOY!
For those of you who gave up looking for the galaxies (bad!), here is the annotated image: