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"
The View Toward M101
21/01/2016
Sweeping through northern skies, Comet Catalina (C/2013 US10) made its closest approach on January 17, passing about 6 light-minutes from our fair planet. Dust and ion tails clearly separated in this Earth-based view, the comet is also posed for a Messier moment, near the line-of-sight to M101, grand spiral galaxy in Ursa Major. A cosmic pinwheel at the lower left, M101 is nearly twice the size of our own Milky Way galaxy, but some 270 thousand light-centuries away. Both galaxy and comet are relatively bright, easy targets for binocular-equipped skygazers. But Comet Catalina is now outbound from the inner Solar System and will slowly fade in coming months. This telescopic two panel mosaic spans about 5 degrees (10 Full Moons) on the sky.