This is the Pinwheel Galaxy M101 or NGC 5457 located in the constellation Ursa Major (The Big Dipper)
M101 is slightly larger than our galaxy with a size of about 170 thousand light years across. It is about 25 million light years away from us. It shines at about magnitude 9.0 and is visible with a good telescope. However to observe the detailed arm structures seen in my image, one requires a very large telescope. I was using a 17 inch Truss scope for this image.
As you can see by the image, M101 is an asymmetrical galaxy. Its spiral arms being forcefully bothered by adjacent neighbouring satellite galaxies.