M101: An Ultraviolet View . ... Credit Copyright: Astro 2, UIT , NASA Explanation: This picture of giant spiral galaxy Messier 101 (M101) was taken by the Ultraviolet Imaging Telescope (UIT). ... The image has been processed so that the colors (dark purple through white) represent an increasing intensity of ultraviolet light . ... Ultraviolet light , invisible to the human eye, is blocked by ozone in the atmosphere so ultraviolet pictures of celestial objects must be taken from space. ...