M101
Messier 101 (M101), also known as the Pinwheel Galaxy, is a face-on spiral galaxy approximately 25 million light-years away in the constellation Ursa Major. Spanning about 170,000 light-years, it is nearly twice the size of the Milky Way and is characterized by its grand design spiral structure.
Source: science.nasa.gov
APODs including "M101"
An Ultraviolet Image of M101
27/06/1995
Today's Picture: June 27, 1995 An Ultraviolet Image of Messier 101 Picture Credit: NASA, Ultraviolet Imaging Telescope (UIT) Explanation: This giant spiral galaxy, Messier 101 (M101), was photographed by the Ultraviolet Imaging Telescope onboard the Space Shuttle Endeavour during the Astro-2 mission (March 2 - 18, 1995). The image has been computer processed so that the colors represent the intensity of ultraviolet light. Pictures of galaxies like this one show mainly clouds of gas containing newly formed stars many times more massive than the sun, which glow strongly in ultraviolet light. In contrast, visible light pictures of galaxies tend to be dominated by the yellow and red light of older stars. 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. For more information see NASA Astro-2 UIT release. We keep an archive of previous Astronomy Pictures of the Day. Astronomy Picture of the Day is brought to you by Robert Nemiroff and Jerry Bonnell . Original material on this page is copyrighted to Robert J. Nemiroff and Jerry T. Bonnell.