M51 galaxy (Whirlpool Galaxy) created in Tagtool live drawing software, with attendant galaxy NGC 5195, which is tugging on the arm as it passes behind M51 In the original NASA image from the Hubble telescope the pink areas are infrared light as well as hydrogen in the giant star-forming areas; blue areas are hot, younger stars, and yellow are the older stars. For illustrating, Tagtool lacks sophisticated brushes (just one solid brush, no feathering or tapering) and masking, but makes up with the ease of use and sheer fun factor, with quick colour selection, quick layer opacity and quick selections/zoom. While you can create better detail using photoshop you have a big advantage in being able to animate each layer instantly in Tagtool ie rotate the arms , blink the stars, have a spaceship float into the scene. So it's my favourite all-round software right now!