M101 - Pinwheel Galaxy
The Pinwheel Galaxy is a face-on spiral galaxy in the constellation of Ursa Major 21 million light years from Earth. At 170,000 light years in diameter, this galaxy is 70% larger than our Milky Way. The dense spiral arms and blue color are the result of gravitational interaction with other galaxies which caused contraction of dust and gasses spurring formation of yourng, hot blue stars. Recent evidence tracking intermediate velocity hydrogen gas pulled from M101 strengthens the case for past interaction with the nearby dwarf galaxy NGC 5474 (just right of this captured field). This interaction likely caused the distortion in the outer spiral arms of M101.