"A digital photograph of the Galaxy Messier 101 (also known as the Pinwheel Galaxy), constructed over the course of three (non-consecutive) years using the Burrell Schmidt Telescope at Kitt Peak National Observatory. The galaxy was imaged four times, using four diff...
"A digital photograph of the Galaxy Messier 101 (also known as the Pinwheel Galaxy), constructed over the course of three (non-consecutive) years using the Burrell Schmidt Telescope at Kitt Peak National Observatory. The galaxy was imaged four times, using four different color light filters: a filter that isolates mostly blue light, one that isolates greenish light, one that isolates mostly red light, and one that isolates a very specific kind of red light emitted mostly by newborn stars. Each of the four images contains around 20 hours of total exposure time. This color image of the galaxy was constructed by layering five different images: the red, green, and blue filter images to create an approximately true-color picture of the galaxy and surrounding environment, an image in which the newborn stars were isolated from the background starlight (seen as the pockets of red throughout the galaxy's spiral arms and elsewhere), and an image of the galaxy that has been heavily processed in order to bring out the faintest starlight at the galaxy's edges (seen as the faint blue 'halo' of light surrounding the galaxy). The latter contains stars that were most likely torn away from the Pinwheel through gravitational interactions with one or more of its neighbors (possibly the smaller galaxy seen near the bottom of the image), and even some very young stars that may have formed through the collapse of extended gas and dust (not pictured) caused by the interaction. The faintest light seen in this image is 1000 times fainter than the dark night sky.
Observations of M101 were done by the following people: Chris Mihos, Paul Harding, Craig Rudick, John Feldmeier, Chelsea Spengler, and Aaron Watkins."