Probably the best example of a spiral Galaxy, M101 is known as the Pinwheel Galaxy for obvious reasons – it’s many spiral arms give a clear impression of a pinwheel. This expansive galaxy is about 27 million light years away from us in the constellation of Ursa Major. M101 is a large galaxy almost double of our Milky Way. With a diameter of 180,000 light-years, it is roughly equal the size of the Milky Way. M101 is so large that its immense gravity distorts smaller nearby galaxies. It’s expected to contain up to a trillion stars. M101 is noted for its high population of Hydrogen nebulae, seen in this image in the pink color.
I took this image over 18.5 hours. There were 14 exposures of 30 minutes each of Luminance and 21 exposure (7 each) of RGB color filters of 20 minutes each. I also added 9 exposures of Hydrogen Alpha (30 min each) to catch prominent nebulae, but, blended that sparingly.